HP 59306A Relay Actuator – front view

HP 59306A "Relay Actuator" (1973)
(click images to enlarge)

HP 59307A VHF Switch – front view

HP 59307A VHF Switch

HP 59501A Isolated Power Supply Programmer – front view

HP 59501A Isolated Power Supply Programmer

The series 59xxx, introduced in 1973/74, were some of Hewlett-Packard's earliest dedicated peripherals for the HP Interface Bus (HP-IB, GPIB, IEEE-488) they had introduced around the same time.
The most intersting aspect of these devices is that they were constructed without the use of microprocessors (even the lowly Intel 8048 would only be introduced in 1976), they were built entirely from SSI TTL ICs.
Remarkably, most of these devices remained in HP's catalogues until the early 1990s.

HP 59301A ASCII Parallel Converter

HP 59303A Digital to Analog Converter

HP 59304A Numeric Display

HP 59306A Relay Actuator

The model 59306 contains six SPDT relays that can be operated through front panel pushbuttons or over the bus.

HP 59307A VHF Switch

The 59307 VHF switch is similar to the 59306 but offers two 4-throw switches with BNC connectors, specified to 500 MHz.

HP 59308A Timing Generator

HP 59309A HP-IB Digital Clock

HP 59313A 4 Channel A/D Converter (1976)

HP 59400A HPIB-RS232/TTY Interface

HP 59401A Bus System Analyzer

HP 59403A Common Carrier Interface

HP 59500A Multiprogrammer HP-IB Interface

HP 59501A Isolated Power Supply Programmer

The 59501 contains a 12-bit digital/analog converter. It was intended to provide an HPIB interface for power supplies with analog remote control terminals, but it can also be used as a stand-alone unit.