US Payphones wiki by telesfor.org

Elcotel 5 was introduced in April 1989. It needs a 6V lead battery to operate, slowly charged from the phone line only when off-hook. Settings and rates are stored in the non-volatile memory (8kB EEPROM) and will not be lost if battery is drained. Programming is done remotely using a modem, it works with 1200 and 300 bps speeds, both Bell and ITU (V.) standards. Lower speed (300 bps) is less reliable, surprisingly. Some basic settings can be done using the keypad, but phone must be programmed remotely in order to operate.

There are two stacked boards, bottom one serving analog / voice / modem purposes and top being a digital control board. Main chips:

• U1: Zilog Z8018006PSC (Zilog) - main CPU, Z80-like (very popular in the 80s with 8-bit computers)
• U2: 27C010, 128kB EPROM - Voice
• U3: 27C512, 64kB EPROM - main firmware
• U4: AT28C64B, 8kB EEPROM - rates and options. Older revisions had a socket, newer are soldered.
• U5: TC551001CP-70L (Toshiba), 128kB static RAM

Digital board also has a piezo ringer (can be enabled or disabled with a jumper next to it) - rather quiet. J4 connector can be used for initializing the board if the button is not present (earlier revisions) and to connect the volume control button (pins 1 & 3, counting from the left). J7 (often times not soldered) - the very bottom - can be used for external power supply. Otherwise, 6V can be supplied in place of the battery. Firmware cannot be flashed remotely, but can be updated in the RAM chip. However, it would revert to the old one in case of battery power loss, sometimes causing major issues - reason is the settings & rates EEPROM contents would be updated to the new firmware, but when rebooted with the old one, they may be incompatible.

Any firmware below 5.3.0 is not NANP compliant.

Voice messages may be supplied in one or two languages. So far we spotted two versions (also refer to firmware). In reality the sound quality is better, this is just a best-guess decode algorithm I made. Notice the synthesized dial tone - doesn't seem to be ever used.
Bilingual, EN-ES
English only, with voice messaging (rare!)

Escrow relay circuit is powered by the line, so if no line voltage of 48V, relay won't work.

Other specs:

• Housing: AE / Quadrum / GTE styles
• Dial/Hookswitch Assy: Elcotel or replica with 17-pin female connector
• Coin Acceptor/Validator: Coinco or Imonex (both require trigger switch) or Mars MS-16 (no option board required)
• Required Coin Relay/Escrow: 48V Coin Relay/Hopper or 48V Dual Solenoid Assy.

Known issues:

• low frequency hum in the receiver on some boards. Reason: unknown

Elcotel 5XG board existed, documented by some GTEL manuals, but no details are known. Probably only the layout was slightly changed.

The oldest boards, from the 1980s. They all can be programmed remotely, as well as (to some extent) locally. Elcotel 3 fits the Western housing, while 1, 2 and 4 - GTE/Quadrum just like the “5”. Rates are stored on a removable, pre-programmed “rates” module (ROM), but new bands can be added remotely. Elcotel 3 and 4 may be equipped with EEPROM chip instead, so all the rates can be updated remotely and stored. Firmware 4.2 was introduced for series 1 - 4 with lots of new features (see documents page) around 1988. Most likely not NANP compliant. Versions 3 & 4 discontinued in Sep. 1992.

This is the latest “retrofit” controller just like Protel 4000/8000. Runs the same firmware as Elcotel 5 and shares the same features. Compatible with Western housings. Elcotel made their own enclosure and keypad assembly, which is not compatible (out of the box) with a standard western 1D or 1C-type keypad, although the round plug is the same. Rework instructions are here. Works with mechanical or electronic coin scanners (DB15 connector), but jumper needs to be set correctly (JMPB at 47A for mechanical, ECM for Electronic). To be updated after I'm done with experiments, just got this unit recently.

When removed from the metal housing, you can see mostly the same components as on Elcotel 5 board, incl. Zilog Z180 CPU and the same buzzer.