Single-slot payphones (placeholder)
In 1965, AT&T introduced its first redesign of the pay telephone — the single slot, flat fronted 1A1. The design remained mostly the same until the 90s. There were a few types of the 1-slot phones, determined by the control board and its 3-character code:
- 1st character: 1 = surface mounted, 2 = flush mounted (panel phone), 3 = electronic*1
- 2nd character: a model code. A = CF only, C = CF/DTF, D = DTF only, E = postpay*2
- 3rd character: 1 = rotary, 2 = Touch Tone, 3 = manual
*1 3A2-3 type was never really seen. Announced in 1984, resembling the Millennium, controlled by microprocessor.
*2 1E types were only made in rotary and manual, not TT.
CF = Coin First (initial deposit was required to hear a dial tone start dialing, usually initiated by a ground start [citation needed]
DTF = Dial Tone First. User can dial the first three digits without a coin (this is controlled by a Central Office equipment). A collection of initial deposit signaled to CO by applying a resistance between Tip and the ground. Initial deposit amount was determined by the mechanical totalizer (A and C type) and electronic totalizer in D (on the controller board).
1A boards: line polarity matters and must not be reversed upon call answer
1C boards had two 11-pin round connectors and all analog circuits, while 1D had one 11-pin (dial unit, headset) and one 13-pin D-sub for totalizer. Released 1972.
Various makes (revisions) existed for each set over time, actual board type for 1C set was 31 series, 1D - 32A/B/C.
1D - 32B board, 1984. Manufactured from late 70s. Notice the mercury relays. There are two “sandwiched” circuit boards, the back side has five dip switches to select the initial rate (5+10+20+40+80, selected: 50ct). 32A board was almost the same, except the dip switch on the back was not present - rate was determined by a wire connection matrix.
1D - 32C board, 1989. The last one from the original 1D series. It only has one layer and the rate switches are on the top. There is a newer version with a MOSFET instead of one of the relays.
Original 1D (“dumb”) boards were only made until certain year[when?]. In the 90s they were being repaired or replaced as needed with “retro-fit” microprocessor boards, mostly Protel 4000 and 8000, Elcotel, GTE Supply and other OEM boards.
1C2 payphone, 1975, 31A board and 20A coin sorter. Mechanical totalizer visible in the middle.
Other 1D2 payphones boards:
- 32D - a hybrid board. Local calls processed by the C.O., long distance - by rate tables. Remotely programmed, had voice prompts etc. Not very popular, introduced in 1996.
- 38A - this is Lucent Technologies - branded, Elcotel 5501 controller.