On this page I will discuss all vintage HP test equipment instruments in numerical order. For reference, the top page of my HP Museum site is kennethkuhn.com/hpmuseum/index.htm. To keep this list from becoming extremely long I have generally omitted accessory items such as adapters, cables, waveguide pieces, etc. The primary focus is on powered equipment. The time period covered is from 1939 to the late 1960's with a few special cases extending to 1990.

Information is taken from my collection of Vintage HP catalogs. In parenthesis beside each number are the years of production to the best I can determine as there are some gaps in my catalog collection. In some cases, information in the HP Journal is used for more precise dating. Also, any references concerning the piece of equipment in the Hewlett-Packard Journal are listed.

The following nomenclature is used for dates:

<1945 means that the instrument was first made prior to 1945. In a few cases, the date is well known such as 1939 for the HP200A so I use well known dates when applicable.

<1952 means that the instrument was first made or discontinued after 1945 but before 1952.

<1955 means that the instrument was first made or discontinued after 1952 but before 1955.

<1959 means that the instrument was first made or discontinued after 1955 but before 1959.

<1961 means that the instrument was first made or discontinued after 1959 but before 1961.

?1949, for example, means that the instrument was first made or discontinued during or before this year.

1962?, for example, means that the instrument was first made or discontinued during or before this year.

~1949 means approximately the year 1949, etc. based on information in Hewlett-Packard Journal or another source. Dating based on the Hewlett-Packard Journal can be off by many months as an article about a piece of equipment might be published months after its introduction but sometimes it was soon. In some cases, date information is provided in the article which definitely makes it easier.

AC-4A Decade Counter (1955 - ). This was a complete decade counter plug-in unit with ten display indicators to indicate the count. It was used in various HP counters such as the HP521 and others. It could count up to 120 kHz.

AC-4B Decade Counter ().

AC-4C Decade Counter (<1959 - ). This counter had a maximum frequency of 220 kHz

AC-4D Decade Counter ().

AC-4E Decade Counter (<1959 - ). This counter had a maximum frequency of 1.2 MHz

AC-4G Decade Counter (<1959 - ). This counter had a maximum frequency of 120 kHz

AC-60A Line Matching Transformer (). This was an accessory transformer that was used to connect an HP200CD or HP400D to a balanced system over the frequency range from 5 Hz to 600 kHz.

AC-60B Line Matching Transformer (). This was an accessory transformer that was used to connect an HP330B to a balanced line. It was just like the AC-60A except that it was optimized for low-distortion audio use and had a frequency response from 20 Hz to 60 kHz.

AC-297C Sweep Drive (<1961 - ). This unit was first developed for use with the HP302A Wave Analyzer and had a motor to drive the main tuning knob and a potentiometer output in proportion to shaft position. The potentiometer output could be used to drive an XY plotter to that a spectrum plot could be made.

AK-60K Matching Transformer (). This was used for impedance matching between hp-485 series barretter mounts and the HP416A/B ratio Meter.

HP100A Frequency Standard (?1941 - ~1949). This was a secondary frequency standard. It generated accurate frequencies at 100 kHz, 10 kHz, 1 kHz, and 100 Hz using a 100 kHz crystal oscillator and frequency dividers. (mention in HPJ Oct. 1949, Vol. 1 #2)

HP100B Frequency Standard (?1941 - ~1949). This was identical to the HP100A except that it included a temperature stabilized oven to keep the 100 kHz crystal at a constant temperature for even better accuracy. (mention in HPJ Oct. 1949, Vol.1 1 #2)

HP100C Frequency Standard (~1949 - ). This unit replaced the HP100A and is the same as the HP100D except that it has less accuracy, no built-in oscilloscope, frequency shift circuit, and does not supply timing markers and rectangular waves. (mention in HPJ Oct. 1949, Vol.1 #2)

HP100D Frequency Standard (~1949 - ). This unit replaced the HP100B and could produce highly accurate 100 kHz, 10 kHz, 1 kHz, 100 Hz, and 10 Hz signals. In addition, each signal except for 100 kHz could be a rectangular wave with useful harmonics up to 5 MHz. A built-in oscilloscope provided Lissajous patterns for checking instrument operation and for comparing to external frequencies. A frequency shift circuit would shift the 100 kHz oscillator by approximately 1 Hz to aid in frequency measurement. (article in HPJ Oct. 1949, Vol. 1 #2)

HP100E Frequency Standard (1961 - ). This unit replaced the HP100D and provided accurate outputs at 10 Hz, 100 HZ, 1 kHZ, 10 kHZ, 100 kHZ, and 1 MHz. A built-in oscilloscope provided Lissajous patterns for checking instrument operation and for comparing to external frequencies.

HP101A 1 MC Oscillator (1961 - ). This was a highly stable 1 MHz oscillator designed for use with the HP5275A Electronic Timer Interval Counter.

HP103AR Quartz Oscillator (1961 - ). This was a temperature stabilized quartz oscillator that provided accurate signals at 1 MHz and 100 kHz. The long term drift was 5 parts in 10¹⁰ per day.

HP104AR Quartz Oscillator (1961 - ). This was the same as the HP103AR but also provided a 5 MHz output that had an extremely pure spectrum. Spectra only a few Hertz wide in the GHz region could be obtained by multiplication of the 5 MHz output.

HP110B Scaler (<1945 - ). This was a external divide by ten or multiply by 10 unit similar to the internal divider of the HP100A/B that was supplied on special order for use with either the HP100A or HP100B. It could generate frequencies down to 10 Hz or up to 1 MHz.

HP113BR Frequency Divider and Clock (1961 - ). This instrument was used for precise comparisons between local frequency standards and broadcast national standards such as WWV.

HP114BR Time Comparator (1961 - ). This was an auxiliary unit used with the HP113BR to provide additional speed and flexibility in making time comparisons.

HP120A Oscilloscope (<1959 - ). This was a single channel triggered sweep oscilloscope that had a vertical bandwidth of 200 kHz and sensitivity of 10 mV/cm to 100 V/cm. The horizontal amplifier also had 200 kHz bandwidth and there was less than 2 degrees of phase difference between vertical and horizontal at 100 kHz.

HP120B Oscilloscope (1963 - ). This was an improvement to the HP120A and had a new CRT with internal graticle for no parallax errors, improved accuracy and a wider bandwidth of 450 kHz.

HP122A Oscilloscope (<1959 - ). This was a dual trace version of the HP120A.

HP130A Oscilloscope (1956 - <1959). This was the first oscilloscope that HP sold.

HP130B Oscilloscope (<1959 - ). This was an improved version of the HP130A and

HP130C Oscilloscope (1963 - ). This was an improvement of the HP130B and had a new CRT with internal graticle for no parallax error, improved accuracy and a wider bandwidth of 500 kHz.

HP140A Oscilloscope (1963 - ). This was an oscilloscope mainframe that accepted both vertical and horizontal plug-ins to configure its function. There were many 1400 series plug-ins as well as 8550 series spectrum analyzer plug-ins available in the late 1960's (the 8550 series plug-ins worked best in a highly shielded mainframe such as the HP141S or HP140T, HP141T).

HP150A Oscilloscope (1956 - ). This was the first wideband oscilloscope that HP sold. It had a vertical bandwidth of 10 MHz and had plug-in vertical units for customized performance.

HP151A High Gain Amplifier (1956 - ). This was a plug-in for the HP150A and featured sensitivity to 5 mV/cm. It had two channels of input although only a single channel could be displayed at a time.

HP151B High gain Amplifier (<1961 - ). This was an improved HP151A unit

HP152B Dual Channel Amplifier (<1959 - ). This was a plug-in for the HP150A and featured dual channels and 50 mV/cm sensitivity.

HP153A Differential Amplifier (<1959 - ). This was a plug-in for the HP150A and featured a differential input with a sensitivity of 1 mV/cm and a pass band of DC to 500 kHz.

HP154A Voltage-Current Amplifier (<1961 - ). This was a two channel unit with one channel for measuring voltage and the other channel for measuring AC current via a clip-on probe (AC-21F current probe).

HP160B Oscilloscope (<1961 - ). This oscilloscope had a bandwidth of 15 MHz and made use of plug-ins to make it more versatile. The mainframe accepted plug-ins for vertical and also had a plug-in section for horizontal accessories.

HP162A Dual Trace Amplifier (<1961 - ). This was a plug-in for the HP160/HP170 series oscilloscopes. It had a sensitivity of 20 mV/cm and a net bandwidth of 14 MHz when used with an HP160 and 25 MHz bandwidth when used with the HP170.

HP162F Fast Rise Preamp (1961 - ). This was a single channel plug-in for the HP160/HP170 series oscilloscopes. It allowed the full bandwidth of the mainframe and had a sensitivity of 50 mV/cm.

HP166B Time Mark Generator (<1961 - ). This was an accessory horizontal plug-in for the HP160/HP170 series oscilloscopes. It provided intensity modulated time markers on the oscilloscope trace.

HP166C Display Scanner (<1961 - ). This was an accessory horizontal plug-in for the HP160/HP170 series oscilloscopes. This unit would sample the oscilloscope trace at a low frequency an provide an output to connect to an XY plotter to plot a copy of the oscilloscope trace.

HP166D Sweep Delay Generator (<1961 - ). This was an accessory horizontal plug-in for the HP160/HP170 series oscilloscopes. This unit provided a second horizontal time base to zoom in on a selected portion of the main sweep.

HP170A Oscilloscope (1961 - ). This oscilloscope was identical to the HP160B except that its vertical bandwidth was 30 MHz.

HP185A Oscilloscope (1961 - ). This was an oscilloscope that used sampling methods to achieve a vertical bandwidth of 1000 MHz. The vertical system was in a plug-in

HP187B Dual Trace Amplifier (1961 - ). This was a plug-in for the HP185A oscilloscope.

HP196A Oscilloscope Camera (<1961 - ). This camera used standard Polaroid film and was made to take pictures of the trace on an oscilloscope screen.

HP200A Oscillator (1939 - 1952). This was the first product of the newly formed Hewlett-Packard Company and was based on the model Mr. Hewlett constructed for his Master's thesis at Stanford University (this model is now at the HP archives and there is a picture of it on their web site - see the main page of my hpmusuem web site for a link to it). The HP200A covered the frequency range from 35 Hz to 35 kHz in three overlapping bands. It could deliver up to about one watt of power into a 500 Ohm load.

HP200B Oscillator (?1940 - 1952). This was an HP200A modified to produce signals about an octave lower. It covered the frequency range from 20 Hz to 20 kHz in three overlapping bands and could deliver up to about one watt of power into a 500 Ohm load.

HP200C Oscillator (1940? - 1952). This was the first high frequency RC oscillator and covered the frequency range from 20 Hz to 200 kHz in four overlapping bands and could deliver up to 10 Vrms into a 1000 Ohm load.

HP200D Oscillator (1940? - 1952). This oscillator covered the frequency range from 7 to 70 kHz in four overlapping bands and could deliver up to 10 Vrms into a 1000 Ohm load.

HP200H High Frequency Oscillator (<1952 - <1952). This was the ultimate in high frequency RC oscillators until the HP650A was introduced. The HP200H (the H stood for high frequency) could produce sine waves from 60 Hz to 600 kHz in four overlapping bands and could deliver about 10 milliwatts to a 100 Ohm load.

HP200I Interpolation Oscillator (<1945 - <1959). This oscillator featured fine frequency settability and the "I" stood for interpolation. This oscillator covered the frequency range from 6 Hz to 6 kHz in 6 overlapping bands of 6 - 20 Hz, 20 - 60 Hz, etc. and could deliver up to a 100 milliwatt signal to a 1000 Ohm load.

HP200J Interpolation Oscillator (<1959 - ). This was an improved version of the HP200I and was also in the new tall style case. The frequency range was 6 Hz to 6 kHz in 6 overlapping bands. It could deliver 10 Vrms to a 600 Ohm load.

HP200S Oscillator ().The HP200S was an HP200CD modified to drive a 50 Ohm load. This oscillator was used primarily for frequency response testing and the "S" referred to response as in the Laplacian "s" used in frequency domain network analysis.

HP200T Telemetry Oscillator (<1959 - ). The "T" refers to telemetry and this oscillator had frequency bands arraigned to conveniently span the telemetry bands that used to be used. The frequency range was 250 Hz to 100 kHz in five overlapping bands. It could deliver 10 Vrms to a 600 Ohm load.

HP200AB Audio Oscillator (1952 - 1975). This oscillator replaced the models 200A and 200B. The case was more compact to make more efficient use of bench space. It covered the frequency range from 20 Hz to 40 kHz in 4 overlapping bands. The highest frequency band was from 4 kHz to 40 kHz and the user had to mentally double the reading on the frequency dial. It could deliver up to about 1 watt into a 600 Ohm load. The oscillator circuit was improved to be a push-pull type which lowered distortion.

HP200CD Oscillator (1952 - 1985). This oscillator replaced the models 200C and 200D. The case was like the HP200AB. It covered the frequency range from 5 Hz to 600 kHz in 5 overlapping ranges and could deliver up to about 160 milliwatts into a 600 Ohm load. This is probably the best known of all of the HP oscillators and had the longest production run.

HP201A Oscillator (???). no evidence has been found that this product ever existed. It is listed here as a place holder.

HP201B Oscillator (1945 - ). This audio frequency sine wave oscillator covered the frequency range from 20 Hz to 20 kHz in three overlapping bands, had fine frequency control, could deliver up to 3 Watts into a 600 Ohm load, and had a dual control attenuator with continuous adjustment over a 40 dB range.

HP201C Audio Oscillator (<1959 - ). This was an improved version of the HP201B and was in the new tall style case.

HP202A Oscillator (1951 - ). This oscillator is based on synthesized sine waves rather RC networks. The synthesis method solved the fundamental problem of generating ultra low frequency sine waves. The frequency range was from 0.01 Hz to 1000 Hz in five overlapping bands. The fundamental oscillator was a triangle wave type. The triangle wave was applied to a non-linear voltage divider comprised of a diode network to shape the triangle wave into an excellent approximation of a sine wave (the distortion was less than 2%). The output of the oscillator was selectable to be either triangle, sine, or square wave. Because amplitude stabilization did not depend on the thermal time constant of a lamp filament there were no amplitude transients when the frequency was changed.

HP202B Oscillator (?1949 - ). With a low frequency limit of 0.5 Hz, this oscillator achieved the lowest frequency of any of the RC oscillator series. To achieve this feat, four each of a four-gang variable capacitor was used for tuning and this array behind the front panel is a very impressive sight. It took three light bulbs in series in order to have a sufficiently long thermal time constant to achieve amplitude stabilization at this low frequency. It covered the frequency range from 0.5 Hz to 50 kHz in 5 overlapping bands and could deliver up to 10 Vrms to a 1000 Ohm load. (article in HPJ Nov. 1949, Vol. 1, #3)

HP202C Low Frequency Oscillator (<1959 - ). The was an improved version of the HP202B and was available in the new tall style case. It covered 1 Hz to 100 kHz in five overlapping bands and could deliver 10 Vrms to a 600 Ohm load.

HP202D Oscillator (?1941 -). This was a cousin of the HP200D oscillator and covered a frequency range from 2 Hz to 70 kHz in 5 overlapping ranges with the highest range covering 7 kHz to 70 kHz, The lower ranges covered 2 Hz - 20 Hz, etc. It could deliver up to 10Vrms to a 1000 Ohm load.

HP203A Variable Phase Oscillator ().

HP204A Audio Oscillator (portable) (<1952 - ). This battery powered oscillator covered the frequency range from 2 Hz to 20 kHz in four overlapping bands and could deliver up to 5 Vrms into a 10,000 Ohm load.

HP204B Oscillator (1961 - ). This was a solid state replacement of the HP204A oscillator that could produce sine waves over the frequency range of 5 Hz to 500 kHz in five overlapping bands. It could produce up to 2.5 Vrms into a 600 Ohm load. It had a continuous constant impedance attenuator range of 40 dB. The unit was intended for battery operation but an internal AC power supply could be installed as an option.

HP204C Oscillator ().

HP204D Oscillator ().

HP205A Audio Signal Generator (?1941 ). This instrument is the same as the HP205AG except that the input vacuum tube voltmeter is eliminated.

HP205AG Audio Signal Generator (?1941 ). This instrument was the ultimate in audio system testing as it was the combination of six instruments: variable audio frequency sine wave oscillator, 5-Watt amplifier, two AC vacuum tube voltmeters, 110 dB attenuator, and matching transformer impedance selector. It covered the frequency range from 20 Hz to 20 kHz in three overlapping bands. Sine wave distortion was less than 1%. The output transformer had taps for 50, 200, 500 and 5000 Ohms. The unit weigh 73 pounds.

HP205AH Supersonic Signal Generator (<1945 ). This instrument was identical to the HP205AG except that it covered the frequency range from 1 kHz to 100 kHz in three overlapping bands.

HP206A Audio Signal Generator (<1952 - ). This oscillator produced sine wave signals over the frequency range from 20 Hz to 20 kHz in three overlapping ranges and with distortion less than 0.1 %. With a tapped transformer it could deliver up to 15 dBm into a selected balanced load impedance of 50, 150 or 600 Ohms. There was an output meter and 111 dB step attenuator in 0.1 dB steps.

HP207A Audio Sweep Oscillator (<1959 - ) This oscillator was based on a complex RC network to achieve a 1000 to 1 frequency range in a single band and also to achieve nearly perfect logarithmic frequency resolution. There was only one frequency band that covered 20 Hz to 20 kHz with each decade of frequency uniformly distributed on the dial. This made the unit ideal for audio frequency response testing.

HP208A Oscillator ().

HP209A Oscillator ().

HP210A Square Wave Generator (?1941 - ). This was a square wave generator that was driven by an external oscillator such as an HP200C. The HP210A would amplify the external sine wave until it was highly clipped. The rise time was less than 1 microsecond. Its best performance was over the 20 to 10,000 Hz range although reasonable square waves up to 100 kHz could be produced. It could produce an output of 60 Volts peak to peak and had a adjustable 70 dB attenuator for producing small signals as well.

HP211A Square wave Generator (1955 -). This square wave generator could produce square waves from 1 Hz to 1 MHz in six bands at an amplitude up to 55 Volts peak to peak across its internal 600 Ohm resistance. Rise time was less than 100 ns.

HP212A Pulse Generator (<1952 - ). This was a basic test instrument for radar, TV, and other fast circuits. The pulse width was continuously variable from 70 ns to 10 us. The amplitude was up to 50 volts into a 50 Ohm load. The pulse repetition rate was variable from 50 to 5000 Hz internally or could be externally controlled.

HP218AR Digital Delay Generator (<1959 - ). This unit was designed to generate precise time intervals and single, double, or superimposed pulses depending on which 219 series plug-in was installed.

HP219A Dual Trigger Unit (<1959 - ). This was a plug-in for the HP218AR and contained two blocking oscillators supplying positive polarity trigger pulses to control auxiliary equipment.

HP219B Dual Pulse Unit (<1959 - ). This was a plug-in for the HP218AR and contained two pulse generators providing digitally delayed, fast rise time, high power pulses.

HP219C Digital Pulse Duration Unit (<1959 - ). This was a plug-in for the HP218AR and produced a high power output pulse with digitally controlled delay and duration.

HP230A Carrier Test Oscillator (1952 - ). This oscillator covered the frequency range from 35 Hz to 35 kHz in three overlapping bands and could deliver up to 4 Vrms to a balanced 600 Ohm.

HP231A Carrier Test Oscillator ().

HP232A Carrier Test Oscillator ().

HP233A Carrier Test Oscillator (1952 - ). This oscillator covered the frequency range from 50 Hz to 500 kHz in four overlapping bands and could deliver up to 3 Watts into a balanced 600 Ohm load. It featured a very large frequency dial with room for many calibration points. It also had an output voltmeter and could be amplitude modulated at voice frequencies.

HP234A Carrier Test Oscillator (1952 - ). This oscillator was identical to the HP230A except that the frequency range was from 160 Hz to 160 kHz.

HP236A Oscillator ().

HP239A Oscillator (). This was the last oscillator that HP produced based on RC networks. This oscillator was also the best - distortion components were over 100 dB below the fundamental. Tuning was accomplished by switches (like the HP241A and HP4204A).

HP241A Oscillator ().

HP300A Harmonic Wave Analyzer (?1941 - ). This was a harmonic wave analyzer which is also known as a tuned voltmeter or manually tuned spectrum analyzer and can measure the signal amplitude within a narrow band around a selected frequency. The continuous frequency range was from 30 to 16,000 Hz and the -3dB bandwidth was continuously variable between 3 Hz and 20 Hz (the dial was calibrated at half the bandwidth at the -40 dB level for a range of 30 Hz to 145 Hz). This was a complicated instrument and took above average knowledge to operate but was capable of measuring signals not possible with any other instrument. It was aimed at audio frequency applications and it was a must have piece of equipment for any serious audio laboratory.

HP302A Wave Analyzer (1959 - ). This was an improved solid state replacement for the HP300A. It was one of the first solid state pieces of equipment HP made. This was a tuned voltmeter or manual spectrum analyzer with a fixed bandwidth of 6 Hz and could be tuned over the range of 20 Hz to 50 kHz. It had full scale meter readings from 30 uV to 300 Volts.

HP320A Distortion Analyzer (?1941 - ). This was a economy distortion analyzer that was based on a passive network to notch out the fundamental at 400 Hz and 5 kHz. It would be used in conjunction with an HP400A AC voltmeter or an oscilloscope to measure distortion down to about 0.1 % in a two step process. First, a signal would be applied at one of the operating frequencies and the notch circuit would be bypassed so that the external meter could measure the total amplitude of the signal including distortion. Then the notch filter would be switched in and a notch adjustment in conjunction with fine frequency control of the signal source would be made to produce the minimum possible reading on the external meter. The ratio of this minimum reading to the un-notched reading multiplied by 100 would indicate the distortion in percent.

HP320B Distortion Analyzer (?1941 - ). This was the same as the HP320A except that it had more notch filters and could measure distortion at 50, 100, 400, 1,000, 5,000, and 7,500 Hz.

HP325B Distortion Analyzer (?1941 - ). This noise and distortion analyzer combined three separate instruments into one: a notch filter, amplifier and vacuum tube voltmeter. It could measure distortion to 0.1 % at 9 switched frequencies from 30 Hz to 15 kHz.

HP330B Distortion Analyzer (<1945 -). This distortion analyzer was a more versatile version of the HP325 unit and with a tuning unit similar to that used in the audio oscillators could measure distortion to 0.1 % at any frequency between 20 Hz and 20 kHz in three overlapping frequency bands.

HP330C Distortion Analyzer (<1952 -). This was the same as the HP330B except that the meter had special ballistic characteristics to meet FCC specifications for FM broadcasters.

HP330D Distortion Analyzer (<1952 - ). This was the same as the HP330C except that an AM detector was included for monitoring AM broadcasts.

HP335B Monitor (<1952 - ). This unit was intended for use by FM stations to monitor the carrier frequency and modulation on the transmitted signal.

HP335C Monitor (<1952 - ). This unit was similar to the HP335B but was intended for use by television stations for channels 2 through 13.

HP340A Noise Figure Meter ().

HP340B Noise Figure Meter (1959 - ). This instrument automatically computed noise figure for a receiver under test. The value was indicated on a meter. The instrument would modulate an external noise source on and off and measure the signal level at the intermediate frequency of the receiver. The two signal values would enable the noise figure to be determined. The HP340B could operate at either 30 or 60 MHz

HP342A Noise Figure Meter (1959 - ). This instrument was the same as the HP340B except that it could operate on 30, 60, 70, 105, and 200 Mhz.

HP343A Noise Source (1959 - ). This was a temperature limited diode noise source that put out broadband noise from 10 to 600 MHz.

HP344A Noise Figure Meter (<1961 - ). This was a noise figure meter specialized for use with radar systems.

HP345B IF Noise Source (1959 - ). This noise source operated at either 30 or 60 MHz and could be matched into 50, 100, 200 or 400 Ohm impedances.

HP347A Waveguide Noise Source (1959 - ). This is actually a family of noise sources for the different waveguide frequency ranges. Each was a Argon gas discharge tube mounted in the waveguide. It was available for all frequencies between 2.6 and 18 GHz. The part number was prefixed with the standard frequency range letter for waveguides: S, G, J, H, X, or P.

HP349A UHF Noise Source (<1961 - ). This noise source had a frequency range of 400 to 4,000 MHz and was for use with the HP340 or HP342 Noise Figure Meters.

HP335E VHF-UHF TV Monitor (<1955 - ). This unit was like the HP335C except that it also could work on UHF TV channels 14 to 83.

HP336C Monitor (<1952 - ). This unit was similar to the HP335B but was intended to monitor the picture carrier frequency of a selected TV channel from 2 through 13.

HP350A Attenuator (<1945 - ) This was an adjustable 110 dB attenuator with both 10 dB and 1 dB steps with a constant impedance of 500 Ohms. It could handle up to 5 watts of input power over a frequency range from DC to over 100 kHz. It was ideal for reducing the output of an HP200 series oscillator.

HP350B Attenuator (<1945 - ) This was identical to the HP350A except that it was designed for a constant impedance of 600 Ohms.

HP355A VHF Attenuator () This 50 Ohm attenuator worked from DC to 500 MHz and provided attenuation from 0 to 12 dB in 1 dB steps.

HP355B VHF Attenuator () This 50 Ohm attenuator worked from DC to 500 MHz and provided attenuation from 0 to 120 dB in 10 dB steps.

HP400A Vacuum Tube Voltmeter (?1941 - <1955) This was an AC vacuum tube voltmeter that had 9 ranges from 0.03 to 300 Volts full scale. The frequency range was 10 Hz to 1 MHz. It had an angled case to make it easier to read the meter.

HP400B Vacuum Tube Voltmeter (<1952 - <1955) this unit was the same as the HP400A except it was designed to work down to 2 Hz. This unit also had output terminals so that it could also be used as a wide band amplifier. It had the same sloping case as the HP400A.

HP400C Vacuum Tube Voltmeter (<1952 - <1955) This was an improved version of the HP400A that could measure from 100 microvolts to 300 Volts over the frequency range of 20 Hz to 2 MHz. This unit had output terminals so that it could be used as a wide band amplifier. It had the same sloping case as the HP400A. A note in the 1955 catalog on page 32 indicates that 10,000 HP400C units were made.

HP400D Vacuum Tube Voltmeter (1955 - ) This unit replace the HP400C and featured a new case design that was vertical. The frequency response was 10 Hz to 4 MHz. It could measure from 1 millivolt to 300 volts full scale in twelve ranges and had output terminals so that it could be used as an amplifier too.

HP400H Vacuum Tube Voltmeter (<1959 - ) This is an HP400D with improved accuracy specifications.

HP400L Vacuum Tube Voltmeter (<1959 - ) This is an HP400D with a logarithmic meter movement so that the dB scale is linear.

HP400AB Vacuum Tube Voltmeter (1955 - ) This unit replaced the HP400A and HP400B and was in the same tall case as the HP400D. It was an economy unit that had a frequency response from 10 Hz to 600 kHz and could measure from 3 millivolts to 300 volts full scale in eleven ranges and had output terminals so that it could be used as am amplifier too.

HP403A AC Transistor Voltmeter (<1961 - ) This was a battery powered, solid state meter that provided similar performance of the 400 series meters. The frequency response was 1Hz to 1 MHz and the full scale voltages ranged from 1 mV to 300 Volts.

HP404A Vacuum Tube Voltmeter (portable) (1952 - ). This unit was battery powered and could measure AC or DC voltage from 3 mV to 300 V full scale in 11 ranges. The AC response was from 2 Hz to 50 kHz. The unit had output terminals so that it could also be used as an amplifier.

HP405AR Automatic DC Digital Voltmeter (1959 - ). This was the first digital voltmeter HP made. It had three digits of resolution and could measure from 0.001 to 999 Volts with automatic ranging. The display was nixie tubes.

HP405BR Automatic DC Digital Voltmeter (<1961 - ). This was a revised version of the HP405AR and operated the same.

HP405CR Automatic DC Digital Voltmeter (<1961 - ). This was a special version of the HP405BR intended for system use. It had provision an external sampling command and had an output interface to an HP560A/HP561B digital recorder.

HP410A Vacuum Tube Voltmeter (<1945 - <1952). This a high frequency vacuum tube voltmeter. It was designed by David Packard. The unit had full scale AC and DC volt ranges of 1, 3, 10, 30, 100, and 300 volts and there was a 1000 volt scale for DC only. The unit could measure resistance from 0.1 to 500 megohms in seven ranges. The frequency response was from 20 Hz to 700 MHz and the probe was usable up to 3 GHz. A special vacuum diode was designed to fit into the probe to provide this wide bandwidth.

HP410B Vacuum Tube Voltmeter (<1952 - ). This was a revised design of the HP410A and had similar specifications. The case appears to be a bit shorter.

HP411A RF Millivoltmeter (1961 - ). This meter used a compensated diode approach to measure 3 mV to 10 Volts over a frequency range of 500 kHz to 1000 MHz. One diode was used to detect the RF signal. Another diode in close thermal proximity detected the level of a 100 kHz signal generated by the meter electronics. An error amplifier drove control electronics that adjust the amplitude of the 100 kHz signal so that the two detected voltages were the same. Then the amplitude of the 100 kHz signal was the same as that of the RF signal.

HP412A Precision Voltmeter (1959 - ). This unit could measure DC voltage and current and also resistance. The DC voltage range was 1 mV to 1000 Volts full scale. The DC current was 1 uA to 1 Amp full scale. The resistance range was 1 Ohm to 100 megohms centerscale.

HP413A DC Null Voltmeter (<1961 - ). This instrument had a large zero center meter and had end scale ranges from 1 mV to 1000 Volts. It had an output connection so that it could also be used as an amplifier.

HP415A Standing wave Indicator (<1952 - ). This instrument is basically a high gain narrow band audio amplifier that is used to measure the output of a crystal or bolometer on a slotted line. By measuring the maximum and minimum signals as the slotted line is adjusted, the standing wave ratio can be measured. The unit typically operated at a narrow band around 1000 Hz but other frequencies from 300 Hz to 2000 Hz could be special ordered. In operation, a signal generator was either AM or pulse modulated at 1000 Hz and fed to one end of the slotted line. The output end of the slotted line was connected to the load whose SWR was going to be measured. The moveable slot had a detector output that was connected to the HP415A. The detector would produce a 1000 Hz demodulated signal whose amplitude was related to the square of the RF signal (at low signal levels, crystal detectors operate as square law detectors). The scale of the HP415A was calibrated in square law so that the user did not have to do any calculations to measure the SWR ratio.

HP415B Standing Wave Indicator (1955 - ). This was an improved version of the HP415A and was in the new tall style case.

HP416A Ratio Meter (1955 - ). This unit directly and automatically computed SWR by measuring (with accessories) both the forward and reflected signals at the same time. This was highly useful in swept measurements and saved considerable manual adjustment that would be required with an HP415A in a swept application.

HP417A VHF Detector (<1952 - ). This instrument was a super-regenerative receiver covering the frequency range from 10 MHz to 500 MHz. It was intended for use with the HP803A VHF Bridge as a null detector. It had a sensitivity of 5 microvolts over the entire frequency range.

HP420A Crystal Detector ( ). This unit could be used to measure RF voltage over the frequency range from 10 MHz to 12.5 GHz. It had a square law characteristic of 0.1 v/mw.

HP420B Crystal Detector (). This was an HP420A with a selected video load resistor and available as a matched pair.

HP425A Microvolt-Ammeter (1959 - ). This meter had a zero center scale to measure both positive and negative quantities. In voltage mode the end scale ranges were from 10 uV to 1 V and in current mode the end scale ranges were from 10 nA to 3 mA.

HP428A Clip-on DC Milliammeter (<1959 - ). This meter measured DC current using a clamp around the wire. The clamp used a modulated flux gate to instrument the DC current. It had six full scale ranges from 3 mA to 1 A.

HP428B Clip-on DC Milliammeter (1961 - ). This was an improved version of the HP428A and featured a larger meter with mirrored scale, full scale sensitivity down to 1 mA and up to 10 Amperes.

HP430B Microwave Power Meter (1952 -1955). This unit had full-scale power indications of 0.1, 0.3, 1, 3, and 10 mw. The unit worked with either 100 or 200 Ohm thermistors or 200 Ohm bolometers. A self balancing bridge maintained the thermistor or bolometer at the set resistance level. RF power applied to the thermistor or bolometer would reduce (or displace) the amount of bridge power required to maintain the set resistance. The displacement power was then indicated on the meter and was equal to the RF power applied.

HP430C Microwave Power Meter (1955 - ). This was an improved version of the HP430B and was in the new tall style case.

HP431A Power Meter (1961 - ). This was a new solid state power meter that replaced the HP430 series and was designed for use with ambient temperature compensated thermistor mounts such as the HP478A. Because of temperature compensation the full scale power level could go down to 10 uW which was a factor of 10 better than before.

HP434A Calorimetric Power Meter (1959 - ). This meter could measure RF power from 10 mW to 10 watts over the frequency range of DC to 12.4 GHz. It was based on a self balancing bridge like the HP430B but the input power was applied to a termination resistor mounted in a stream of oil. A comparison load resistor was heated by a DC source to match the power dissipated in the termination resistor. Thermistors sensed the thermal mismatch between the two resistors and control electronics adjusted the DC source until balance was achieved. The DC power was then read on the meter and was equal to the RF power.

HP450A Amplifier (1947 - ). This amplifier had a switchable gain of either 20 or 40 dB and operated from 10 Hz to 1 MHz. It could deliver up to 10 Vrms into a 3,000 Ohm load or higher.

HP451A Bridging Amplifier (1952 - <1955). This amplifier had a very high input impedance of 83 megohms and had a voltage gain of 1 and a frequency response of 20 Hz to 1 MHz. It was intended to electronically transform a voltage at a high impedance into the same voltage at a low impedance.

HP452A Capacitive Voltage Divider (<1952 - ). This was a unit to enable the HP400C or HP410B to measure Ac voltages up to 25 kV.

HP453A Capacitive Voltage Divider (<1952 - ). This was a probe accessory for the HP410B to measure high frequency AC voltages up to 2000 Volts.

HP454A Capacitive Voltage Divider (<1952 - ). This was a probe accessory for the HP400C to measure high frequency AC voltages up to 1500 Volts.

HP455A Probe Coaxial "T" Connector (<1952 - ). This was an adapter that allowed the high frequency probe of the HP410B to be inserted into a coaxial line with minimum disturbance to the line.

HP456A AC Current Probe (<1961 - ). This unit had a clip-on probe and amplifier electronics and enabled the HP400 series meters to measure AC current. The unit provided 1 mV per milliampere of current up to a maximum of 1 Ampere.

HP457A AC-DC Converter (<1961 - ). This was an accessory for the HP405 series digital voltmeters that was a precision rectifier so that AC voltages at frequencies up to 500 kHz could be measured. The unit was very general purpose and would work well with any other DC equipment. The scale factor of the output was a 0 - 1 Volt signal corresponding to the rms value of a sine wave applied to the input. The input had manually switched full scale ranges of 1, 10, 100, and 1000 volts rms.

HP458A Probe Coaxial "N" Connector (<1952 - ). This accessory adapted the HP410B high frequency probe to a standard "N" connector.

HP459A DC Resistive Voltage Multiplier (<1952 - ) This probe enabled the HP410B to measure DC voltages up to 30,000 Volts by attenuating the voltage by a factor of 100.

HP460A Amplifier (<1952 - ). This amplifier had a Gaussian bandwidth of 140 MHz and had a voltage gain of about 20 dB with a 6 dB gain adjustment range. It was intended for operation in 200 Ohm circuits.

HP460B Amplifier (<1952 - ). This unit is similar to the HP460A except that it can deliver higher output voltage or power but at a lower gain of about 15 dB. The unit was capable of directly driving the deflection plates of a cathode ray tube.

HP466A AC Amplifier (<1961 - ). This amplifier could provide either 20 or 40 dB voltage gain over the frequency range of 10 Hz to 1 MHz. It normally operated on AC power but had an option to run on batteries.

HP470A - F Shunt Resistors (<1952 - ). This was a series of precision resistors mounted inside a feedthru dual banana jack and was intended for use with the HP400A or HP400C voltmeters. These shunts permitted the meters to measure current by measuring the voltage drop across the resistor. The "A" unit was 0.1 Ohms, the "B" unit was 1.0 Ohms, the "C" unit was 10.0 Ohms, the "D" unit was 100 Ohms, the "E" unit was 600 Ohms, and the "F" unit was 1000 Ohms.

HP475B Tunable Bolometer Mount (<1952 - ). This unit was used to measure power over the 1 GHz to 4 GHz frequency range. It used two tuning stubs to match a 50 Ohm source impedance up to the 200 Ohm impedance of a typical bolometer (a special 1/100-ampere fuse). It was used in conjunction with an HP430B microwave power meter that would sense RF power on the bolometer.

HP476A Universal Bolometer Mount (<1952 - ). This unit was used to measure power over the 10 MHz to 1 GHz frequency range using four 1/100 ampere bolometer elements (200 Ohms each) connected in a series/parallel network so that the RF source saw 50 Ohms but the power meter saw 200 Ohms.

HP477A Thermistor Mount (1955 - ). This was a thermistor mount for use with the HP430C and contained two 100 Ohm thermistors connected in a network such that the RF signal saw 50 Ohms and the HP430C saw 200 Ohms. The unit was usable from 10 MHz to 10 GHz.

HP477B Thermistor Mount ( <1959 - ). This was a newer version of the HP477A thermistor mount.

HP478A Thermistor Mount (1961 - ). This was an extension of the HP477B Thermistor mount and included a pair of thermistors for ambient temperature compensation. The unit was designed for use with the new HP431A power meter.

HP489A Traveling Wave Tube Amplifier (<1961 - ). This amplifier worked of the 1 - 2 GHz frequency range and provided at least 30 dB gain and an output power of 1 watt or more.

HP490A Traveling-Wave Tube Amplifier (1955 - <1959). This amplifier worked over the 2 to 4 GHz frequency range and provided at least 35 dB gain and an output power of 10 mw or more.

HP490B Traveling-wave Tube Amplifier ( <1959 - ). This was an improved instrument that superseded the HP490A

HP491A Traveling-Wave Tube Amplifier (1955 - ). This amplifier worked over the 2 to 4 GHz frequency range and provided at least 30 dB gain and an output power of 1 watt or more.

HP491C Traveling-Wave Tube Amplifier (<1961 - ). This was a revised version of the HP491A amplifier that was in a rack-mount case.

HP492A Traveling-Wave Tube Amplifier (<1959 - ). This amplifier worked over the 4 to 8 GHz frequency range and provided at least 30 dB gain and an output power of 10 mw or more (later revised to 20 mw).

HP493A Traveling-Wave Tube Amplifier (<1961 - ). This amplifier worked over the 4 to 8 GHz frequency range and provided at least 30 dB gain and an output power of 1 watt or more.

HP494A Traveling-Wave Tube Amplifier (<1959 - ). This amplifier worked over the 7 to 12.4 GHz frequency range and provided at least 25 dB gain and an output power of 5 mw or more (later revised to 20 mw).

HP495A Traveling-Wave Tube Amplifier (<1961 - ). This amplifier worked over the 8.2 to 12.4 GHz frequency range and provided at least 30 dB gain and an output power of 1 watt or more.

HP500A Electronic Frequency Meter (?1941 - 1955). This was an electronic frequency meter and indicated frequency on an analog meter over the range of 5 Hz to 50 kHz. with full scale ranges of 50, 100, 200, 500, 1000, 2000, 5000, 10000, 20000, and 50000 Hz. It worked by converting each zero crossing of the input signal frequency to a fixed width pulse train whose average value was linearly related to the frequency.

HP500B Electronic Frequency Meter (1955 - ). This was an improved replacement for the HP500A. It worked from 1Hz to 100 kHz and also had an expanded scale mode that permitted greater resolution. It was in the new tall style case.

HP500C Electronic Tachometer Indicator (1955 - ). This was an improved replacement for the HP505A/B and was identical to the HP500B except that the meter was calibrated for rpm.

HP505A Electronic Tachometer (<1945 - 1955). This was the same as the HP500A but was specialized for measuring the RPS (revolutions per second) of a rotating device and was called an electronic tachometer. A phototube picked up light pulses and the frequency was measured.

HP505B Electronic Tachometer (<1945 - 1955). This was the same as the HP505A except that the scale was calibrated in RPM (revolutions per minute)

HP506 Optical Tachometer Pickup (1947 - ).

HP508A Tachometer Generator (<1955 - ). This was a mechanical tachometer generator for measuring from 15 to 40,000 RPM. It produced 60 cycles per rotation of the shaft for direct RPM indication on a frequency meter.

HP508B Tachometer Generator (<1955 - ). This was identical to the HP508A except that it produced 100 cycles per rotation of the shaft.

HP508C Tachometer Generator (<1959 - ). This was identical to the HP508A except that it produced 120 cycles per rotation of the shaft.

HP508D Tachometer Generator (<1959 - ). This was identical to the HP508A except that it produced 360 cycles per rotation of the shaft.

HP510A Mixer (<1952 - ). This unit was used to mix (multiply) any two frequencies in the 20 Hz to 200 kHz range. It was intended for use with the HP500A or HP100C/D. An adjustable low-pass filter could used to select only the difference frequency output of the mixer.

HP512A Frequency Converter (<1955 - ). This unit was intended for use with an HP524A counter to extend frequency measurement up to 100 MHz by down converting a selected 10 MHz range to the 0 to 10 MHz range of the HP524A.

HP512B Frequency Converter (<1955 - ). This unit was intended for use with an HP524A counter to extend frequency measurement from 100 MHz to 220 MHz by down converting a selected 10 MHz range to the 0 to 10 MHz range of the HP524A.

HP520A High Speed Scaler (1952 - ). This unit (which was included in the HP524A) could scale a frequency or a pulse train downwards by a factor of 100 and had two analog meters to indicate the count.

HP521A Electronic Counter (1955 - ). This was an economy counter that indicated frequency up to 120 kHz with four 0 - 9 display units.

HP521C Electronic Counter (<1959 - ). This was the same as the HP521A except that it had five display units and had a crystal controlled timebase.

HP521D Electronic Counter (<1959 - ). This was the same as the HP521A except that it had four nixie tube digits instead of four 0-9 display units.

HP521E Electronic Counter (<1959 - ). This was the same as the HP521C except that it had five nixie tube digits instead of five 0-9 display units.

HP521G Electronic Counter (<1961 - ). This was the same as the HP5221C except that it could measure up to 1.2 MHz.

HP522A Electronic Counter (1952 - <1955). This unit is a reduced function version of the HP522B. Its gate time is 1 second only, the decimal point register is omitted, and there is no provision for time or interval measurement.

HP522B Electronic Counter (1952 - ). This unit could measure frequency up to 100 kHz and indicated frequency on five 0-9 indicators. It could also measure period from 0.00001 Hz to 10 kHz and measure time interval from 10 us to 100,000 seconds. It could also measure the ratio of two external frequencies.

HP523BR Electronic Counter (<1959 - ). This counter could measure frequency between 10 Hz and 1.2 MHz.

HP523CR Electronic Counter (1959 - ). This counter was an improved HP523BR and featured six nixie tube digits instead of the 0-9 neon indicators.

HP523DR Electronic Counter (1959 - ). This counter was identical to the HP523CR except that it had six banks of 0-9 neon indicators instead of nixie tubes for the frequency readout.

HP524A Frequency Counter (1952 - 1955 ). This was the first HP unit to use digitally counters for measuring frequency. It could measure a frequency up to 10 MHz using six 0-9 indicators and two analog meters.

HP524B Electronic Counter (1955 - ). This unit replaced the HP524A and added the feature of a plug-in for expanded functions. The unit without a plug-in had the same basic specifications as the HP524A.

HP524C Electronic Counter (1959 - ). This was an improved HP524B unit and featured eight digits of nixie tube readout instead of the six banks of 0-9 neon indicators and two analog meters.

HP524D Electronic Counter (1959 - ). This was identical to the HP524C unit except that it had eight banks of 0-9 neon indicators instead of nixie tubes.

HP525A Frequency Converter (1955 - ). This was a plug-in for the HP524B and extended frequency measurement up to 100 MHz by down converting a selected 10 MHz range to the 0 to 10 MHz range of the mainframe unit.

HP525B Frequency Converter (1955 - ). This was a plug-in for the HP524B and extended frequency measurement from 100 MHz to 220 MHz by down converting a selected 10 MHz range to the 0 to 10 MHz range of the mainframe unit.

HP525C Frequency Converter (<1961 - ). This was a plug-in for the HP524 series counter and extended frequency measurement from 100 to 510 MHz by down converting a selected 10 MHz range to the 0 to 10 MHz range of the mainframe unit.

HP526A Video Amplifier (1955 - ). This was a plug-in for the HP524B and provided amplification that extended the sensitivity of the HP524B down to10 millivolts.

HP526B Time Interval Unit (1955 - ). This was a plug-in for the HP524B and enabled time measurement from 1 microsecond to 100 days.

HP526C Period Multiplier Unit (<1959 - ). This was a plug-in for the HP524C.

HP526D Phase Unit (1961 - ). This was a plug-in for the HP524 series counter and enabled precise phase angle measurements from 1 Hz to 20 kHz.

HP540A Transfer Oscillator ().

HP540B Transfer Oscillator (1959 - ). This was an improved HP540A unit.

HP560A Digital Recorder (<1959 - ). This was a data printer that could print 11 digit information up to 5 times per second from equipment that had a digital output option. Typical equipment would be digital voltmeters counters, etc. The HP560A also featured a analog output that could convert any selected three digit group to a voltage that could be recorded on a plotter. The three digit group could be fine resolution digits for highly expanded analog output.

HP561A Digital Recorder (<1959 - ). This was similar to the HP560A except for the interface and the analog output option was omitted.

HP561B Digital Recorder (<1959 - ). This was similar to the HP560A except for the interface and the analog output option was omitted.

HP562A Digital Recorder (1961 - ). This was a transistorized version of the HP560A and was intended for use with the new transistorized electronic counters.

HP565A Digital Printer (1961 - ). This was a separate printer mechanism like the one used in the HP562A unit but was for custom use in non-HP systems.

HP570A Digital Clock (1961 - ). This was a plug-in for the HP560A digital recorder to add time of day stamps to the printed data.

HP571A Digital Clock (1961 - ). This was the same as the HP570A but was a plug-in for the HP561B digital recorder.

HP606A Signal Generator (1959 - ). This generator could produce signals at frequencies from 50 kHz to 65 MHz in six overlapping bands. The output could be amplitude modulated up to 100 %. There were two meters to indicate output voltage and modulation level. An attenuator adjusted the output level from 3 Vrms down to 0.1 uVrms.

HP608A VHF Signal Generator (<1952 - <1955 ). This instrument could generate a 0.1 uV to 1 V signal over the range of 10 MHz to 500 MHz in five overlapping bands. It could be amplitude modulated up to 90 %.

HP608B VHF Signal Generator (1952 - <1955 ). This instrument was very similar to the HP608A except that the highest frequency is 400 MHz and had lower incidental FM.

HP608C VHF Signal Generator (<1955 - ). This generator could generate signals from 0.1 uV to 1 volt over the frequency range of 10 MHz to 480 MHz in five bands and could be amplitude modulated up to 95 %.

HP608D VHF Signal Generator (<1955 - ). This premium quality generator could generate signals from 0.1 uV to 0.5 volts over the frequency range of 10 MHz to 420 MHz in five bands and could be amplitude modulated up to 95 %.

HP610A UHF Signal Generator (1947 - <1952).

HP610B UHF Signal Generator (<1952 - <1952).

HP612A UHF Signal Generator (1952 - ). This unit replaced the HP610 and generated signals from 0.1 uV to 0.5 V over the range of 450 MHz to 1,200 MHz. It could be amplitude modulated up to 90%.

HP614A UHF Signal Generator (<1952 - ). This unit generated signals over the frequency range from 800 MHz to 2,100 MHz. It could be pulse modulated either internally or externally or internal FM modulation at the power line frequency could be used.

HP616A UHF Signal Generator (<1952 - ). This unit generated signals over the frequency range from 1.8 GHz to 4.0 GHz. It could be pulse modulated either internally or externally or internal FM modulation at the power line frequency could be used.

HP616B UHF Signal Generator (<1961 - ). This was a revised HP616A unit.

HP618A SHF Signal Generator (<1952 - 1952).

HP618B SHF Signal Generator (1952 - ). This unit generated signals over the frequency range from 3.8 GHz to 7.6 GHz. It could be pulse modulated either internally or externally or internal FM modulation could be used at an adjustable sweep rate. Additionally, external FM could be applied.

HP620A SHF Signal Generator (1955 - ). This unit was a higher frequency version of the HP618B and generated signals over the frequency range from 7 GHz to 11 GHz.

HP623B SHF Test Set (<1952 - ). This unit operated over a selected 300 MHz band between 5.925 GHz and 7.725 GHz.It could be pulsed or FM modulated. The unit was specialized for certain types of receiver and transmitter testing.

HP624B SHF Test Set (<1952 - <1955. This unit operated over a frequency range of 8.5 GHz to 10.0 GHz. IT could be pulsed or FM modulated. The unit was specialized for certain types of receiver and transmitter testing.

HP624C SHF Test Set (<1955 - ). This unit was just like the HP624B except that it was in a new style case.

HP626A SHF Signal Generator (<1959 - ). This unit generated signals over the frequency range from 10.0 to 15.5 GHz. It could be pulse or FM modulated either internally or externally. Output power was adjustable from 10 mW down to 1 nW.

HP628A SHF Signal Generator (<1959 - ). This unit generated signals over the frequency range from 15.0 to 21.0 GHz. It could be pulse or FM modulated either internally or externally. Output power was adjustable from 10 mW down to 1 nW.

HP650A Test Oscillator (1952 - ). This oscillator covered the frequency range from 10 Hz to 10 MHz in 6 overlapping bands. The 1 MHz to 10 MHz range was a separate oscillator using a new RC circuit capable of higher frequency oscillation than the standard Wein Bridge circuit in the other HP oscillators. Output power was up to 15 millwatts into a 600 Ohm load. This unit also featured an output meter and 50 dB step attenuator.

HP651A Oscillator ().

HP652A Oscillator ().

HP654A Oscillator ().

HP670HM SHF Swept Frequency Oscillator (1955 - ). This oscillator was swept via mechanical means and could be set to sweep any frequency range from 7 GHz to 10 GHz. It could produce 10 milliwatts of output power. The sweep rate was from 12 to 60 cycles per minute. The HP717A klystron power supply was required for operation.

HP682C Sweep Oscillator (1961 - ). A backward wave oscillator was used and could be swept from 1 to 2 GHz at an adjustable sweep rate and width. The oscillator could be either amplitude, frequency, or pulse modulated. Output poer was adjustable from 0 to 10 mw.

HP683A Sweep Oscillator (<1959 - ) . A backward wave oscillator was used and could be swept from 2 to 4 GHz at an adjustable sweep rate and width. The oscillator could be either amplitude, frequency, or pulse modulated. Output power was adjustable from 0 to 10 mW.

HP683C Sweep Oscillator (<1961 - ). A newer version of the HP683A

HP684A Sweep Oscillator (1959 - ). This was identical to the HP683A except that the sweep range was 3.7 to 5.9 GHz.

HP684C Sweep Oscillator (<1961 - ). A newer version of the HP684A

HP685A Sweep Oscillator (<1959 - ). This was identical to the HP683A except that the sweep range was 5.2 to 8.3 GHz.

HP686A-H01 Sweep Oscillator (<1959 - ). This was identical to the HP683A except that the sweep range was 7 to 11 GHz.

HP686C-H01 Sweep Oscillator (<1961 - ). A newer version of the HP686A-H01

HP686A Sweep Oscillator (<1959 - ). This was identical to the HP683A except that the sweep range was 8.2 to 12.4 GHz.

HP686C Sweep Oscillator (<1961 - ). A newer version of the HP686A

HP687A Sweep Oscillator (1959 - ). This was identical to the HP683A except that the sweep range was 12.4 to 18 GHz.

HP687C Sweep Oscillator (1961 - ). A newer version of the HP687A

HP710A Power Supply (<1945 - <1955). This was a power supply unit and could produce regulated output voltages from 180 to 360 Volts at load currents up to 100 milliamperes. The output was floating so either terminal could be grounded to make either positive or negative voltages. A 6.3 VAC filament transformer output was also provided for convenience.

HP710B Power Supply (<1955 - ). This was an improved version of the HP710A and extended the output voltage range from 100 to 360 Volts.

HP711A Power Supply (1955 - ). This power supply could provide 0 to 500 Volt output at up to 100 mA. It had two meters to indicate voltage and current and also had a 6.3 VAC center-tapped filament transformer that could supply up to 5 Amperes.

HP712A Power Supply (1952 - 1955). This power supply could deliver 0 - 500 Volts at up to 200 milliamperes and could deliver 0 - 150 Volts at up to 5 milliamperes for biasing. In addition, it had a 6.3 VAC center-tapped filament supply output at up to 10 amperes. It had two large meters to indicate voltage and current.

HP712B Power Supply (1955 - ). This power supply was a improved version of the HP712A.

HP715A Klystron Power Supply (1952 - ). This was a specialized power supply for operating many different types of low-power klystrons. Supply 1 (beam) output was from 250 to 400 Volts at up to 50 milliamperes. Supply 2 (reflector) output was from 0 to 900 Volts at up to 10 microamperes. It also had a 6.3 VAC filament supply that could suplly up to 1.5 Amperes. Supply 2 could be modulated either internally or externally.

HP717A Kystron Power Supply ( 1955 - ). This unit was similar to the HP715A except that it was specifically designed to control the klystron in the HP670HM SHF Swept Oscillator.

HP721A Power Supply (1959 - ). This was the first solid state piece of equipment that HP made. It was designed specifically for use with transistor circuits. The output voltage could be varied from 0 to 30 Volts and it could supply up to 150 mA. A switchable current limit provided limit values of 25, 50, 100, and 225 mA. A single meter was used to measure voltage or current output.

HP722AR Power Supply (1961 - ). This power supply could deliver 0 to 60 Volts at up to 2 Amperes. It featured two meters to monitor voltage and current. It also had an adjustable current limit.

HP723A Power Supply (1961 - ). This power supply could deliver 0 to 40 Volts at up to 500 milliamperes. It had a variable short circuit current limit. It had a single meter that could monitor either voltage or current.

HP724BR Standby Power Supply (1961 - ). This was a battery backup system that could be used with the HP103AR, HP104AR, or HP113BR units to prevent AC power outages from affecting frequency stability.

HP725AR Standby Power Supply (1961 - ). This was a lower capacity version of the HP724BR.

HP738AR Voltmeter Calibrator (<1961 - ). This unit provided accurate voltages from 300 uV to 300 Volts DC or AC (rms and peak-peak). The AC frequency was 400 Hz.

HP739AR Frequency Response Test Set (<1961 - ). This was an oscillator with a frequency range of 300 kHz to 10 MHz in three bands. It provided accurate output voltages of 0.001, 0.003, 0.01, 0.03, 0.1, 0.3, 1.0, and 3.0 Volts rms.

HP803A VHF Bridge (<1952 - ). This instrument could measure complex impedance over the 52 to 500 MHz range. It was a passive instrument and measured impedance by simultaneous sampling of the electric and magnetic field in its internal transmission line. A magnitude control adjusted two attenuators, one responded to voltage and the other responded to current. The output of the two attenuators was applied to different ends of the internal transmission line. A phase control adjusted the location of a tap on the transmission line. The tap signal was fed to an external null detector (typically the HP417A VHF detector. The magnitude and phase controls were adjusted until a null was found and the complex impedance was read on the two dials. Signal frequency was typically applied using an HP608 VHF Generator.

HP805A Slotted Line (<1952 - ). This unit could be used to measure SWR over the frequency range from 500 to 4,000 MHz.

HP938A Frequency Doubler Set (1961 - ). This unit supplies power from 18 to 26.5 GHz when driven by a 9 to 13.25 GHz source. The unit was designed for 10 mW input power and could supply up to 100 mW of output power.

HP940A Frequency Doubler Set (1961 - ). This unit supplies power from 26.5 to 40 GHz when driven by a 13.25 to 20 GHz source. The unit was designed for 10 mW input power and could supply up to 100 mW of output power

HP4204A Oscillator ().

HP5512A Electronic Counter (1961 - ). This was a solid state counter that could measure frequency up to 300 kHz. It could be purchased with either five 0-9 column indicators or five nixie tube digits.

HP5232A Electronic Counter (1961 - ). This was a solid state counter that could measure frequency up to 1.2 MHz. It could be purchased with either five 0-9 column indicators or five nixie tube digits.

HP5275A Time Interval Counter (1961 - ). This was a solid state that could measure the time interval between two events. It had a resolution of 10 ns and had seven 0-9 column indicators that indicated the time in microseconds.