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, made obsolete by texting. Basically, when someone types on a TTY it sends signals 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. 

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 calling mode on, which allows the smartphone to become a TTY. 

To use a payphone TTY:

1. Dial and pay for call as normal, leave handset off hook. The number you call must be a cell phone with TTY/RTT mode on, or a landline with a TTY unit.

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

3. Start typing, press"GA", press return when your message is done - like a chat room or texting.

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

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.