Payphone Teletypewriter

I had no idea how a Teletypewriter or TTY worked until I saw them on payphones. They are communication devices for the deaf, to type messages over phone lines, but they were made obsolete by texting. Basically, when someone types on a TTY it sends signals (Baudot) down a phone line, where another TTY decodes them back into text. Payphone TTYs work the same way, except you have to pay, of course, and some modifications to take the abuse of constant public use. 

I saw payphone TTYs and thought it would be fun to be able to "text" a smartphone through a payphone. The smartphone needs TTY/RTT (Real Time Text) calling mode on, which allows the smartphone to become a TTY. 

To use a payphone drawer style TTY:

1. Dial and pay for call as normal, leave handset off hook (on shelf, or handset holder is there is any). The number you call must be a cell phone with TTY/RTT mode on, or a landline with a TTY unit to answer the call.

2. When other person starts typing on their TTY, the drawer automatically opens and the TTY turns on.

3. Start typing and have your conversation. Press"GA" after each of your messages - like pressing "Send" in a chat room or texting. GA stands for Go Ahead.

4. When done type "SK", hang up the handset, and the drawer automatically closes. SK stands for Stop Keying.

Traditionally, when messaging through a TTY, after you're done with your one line, you type "GA" which stands for "Go ahead." this lets the other person know it's their turn to start typing.  "SK" stands for "Stop Keying", this is sort of a "Goodbye" and the call ends. 

The keyboard is a completely metal chiclet keyboard, it looks very industrial on its own, and with the vacuum fluorescent display, it looks straight out of the Matrix.

So I bought a used payphone TTY, but it has a slight issue: the drawer opens and closes in cycles whenever something happens on the phone line, such as a call, handset is picked up, etc. It doesn't stop until about 7~ or so in and out cycles, even when calling another TTY like intended. My solution is to just unplug the motor, but it still tries to open and close, even though it can't; you can hear the relays inside clicking.

September 7th, 2026 UPDATE: I've acquired another drawer style TTY, this one h*Some of My Favorite Payphones*

as similar issues, but not as bad. When a TTY call is placed, the drawer goes out, and then in half way, instead of in and out repeatedly. I've been switching parts between the two units, and I've determined that the drawer position switch is bad on both; I'm waiting on a replacement switch to come in the mail. 

The 2nd payphone TTY I've got also has the same screen and functions, but a slightly different keyboard housing; the metal is painted gray, and the keys have the letters printed on them, rather than above them. Both are from 1992.

Spetember 10th, 2026 UPDATE: I've found the issue with my TTY; it was missing a little metal rod, about 1.5," that holds the drawer in the opened or closed position. It's not the drawer position switch. The position switch isn't what tells the board to turn off the motor like I thought; it runs the motor on a timer and then turns it off. The interface board (which connects the power and phone line to the motherboard,) was bad and caused the drawer to go in and out repeatedly. I'll add pictures once I fully reassemble it.

October 11th, 2026 UPDATE: I fixed them both! I repaired the drawer position switch, and added the metal rods that keep it closed. Here are some pictures. I've also built a wooden enclosure, so I can sit the payphone on top.