(516F-2 power supply, 75S-3B receiver, 32S-3 transmitter, 312B-4 console, SM-1 microphone)
https://en.wikipedia.org/wiki/Rockwell_Collins
With the introduction of the S/Line in 1958, Collins moved from designing individual products that could be used together, to ones that were designed to integrate and operate together, in various combinations, as a system. They were the first equipment maker to take this approach. Collins was also the first to introduce a compact HF transceiver, the KWM-1, the year before. Together, these two innovations put Collins temporarily ahead of its competition and set the stage for other manufacturers and the next generation of amateur (and military) HF radio equipment.
The 75S-1 receiver and 32S-1 transmitter, comprising the heart of the S/Line, operated separately or together to transceive. The units included crystal bandpass filters and a new compact PTO design that provided stable, highly linear tuning across 200 kHz band segments. The S/Line tuning dial mechanism was unique when introduced. It used concentric dials and a gear mechanism that provided precise dial resolution, better than 1 kHz.
Within a few years Collins had introduced additional S/Line components, including the 30S-1 kilowatt power amplifier, the 30L-1 desktop power amplifier, and the 62S-1 transverter, which provided coverage of the 6 meter (50 MHz) and 2 meter (144 MHz) amateur bands. The KWM-2 transceiver replaced the KWM-1 using many of the S/Line’s design features and matching its styling. Other accessories included speakers, microphones and control consoles.
Illustrating the uniqueness of their new, smaller units in the market, Collins advertisements in the 1950s and early 1960s emphasized the S/Line’s physical styling and size as often as they did its performance.
Collins continued to improve the S/Line, first introducing the S-2, then the S-3 units, the 75S-3 (and -3A, -3B and -3C) receiver, and the 32S-3 and -3A transmitters. The -3A and -3C units were identical to the -3 and -3B units, respectively, except they provided an extra set of heterodyne oscillator crystals enabling them to cover extra bands – useful for military, amateur and MARS operation, where operation just outside the regular amateur bands was necessary.
Among amateur radio operators, the S/Line established its reputation as perhaps the most solidly engineered equipment available – and the most costly. As a result, S/Line equipment, and the A-Line and other predecessors, are restored, prized, and operated on the air by collectors today.
Collins continued to produce the S/Line well into the late 1970s and after its acquisition by Rockwell.
In 1978, with the move to solid state design, the S/Line came to an end after a two decade production run. The KWM-380 transceiver was introduced the next year – a break with the past both in its use of transistors and digital technology, and its styling. It would be Collins’ final entry in the amateur radio market until it was discontinued in the mid-1980s.