Peripherals
Supervision and trunk signalling were the responsibility of trunk circuits. The most common kinds (reverse battery one-way trunks) were in plug-in trunk packs, two trunks per pack, 128 packs per Trunk Frame (originally) on 16 shelves. Each trunk pack was originally about 3x5x8 inches (8x12x20 cm) with edge connector in the back. The later 1AESS were made with shorter wire spring relays, making them less than half as wide, with more complex leaf spring connector. Trunk Frames were in pairs, the even numbered one having the Signal Distributor to control the relays in both. Most trunks had three wire spring relays and two scan points. They could supply regular battery or reverse battery to a line, and on-hook or off-hook supervision to the distant end, or be put into a bypass state allowing all functions (usually sending and receiving address signals) to be performed by common control circuits such as digit transmitters and receivers. Slightly more complex trunks, for example those going to TSPS offices for operator control, were packaged as only one per plugin unit.
Junctor Circuits were installed in similar frames, but were simpler, with only two relays. They were used only in Line to Line junctors. Large offices, in addition to these Junctor Circuits, had Intraoffice Trunks, which were of similar design but fit into the same Universal Trunk Frames as interoffice trunks. They carried overflow traffic when the small Junctor Groups of an office with many LN could not cope. Digit transmitters, receivers, other complex service circuits, and some complex trunks including those using E&M signaling, were permanently mounted in relay racks similar to those of 5XB rather than plug-in frames.
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