Teletypes in Switzerland were ITU V.21 with three modifications:
- 110 baud instead of 300 baud
- not full duplex
- carrier tone
I experimented with a Java application and FFT to try to write a soft modem, so I still know the exact specification by heart. Bit 1 was 960 Hz, Bit 0 was 1160 Hz, the carrier tone 1060 Hz, and there were 2 stop bits. This means, the teletype could transmit 11 letters a second.
The carrier tone is special: if someone stopped typing, the teletype switched to the carrier tone and kept it on for about 3 seconds then stopped.
Being not full-duplex Deaf users used a convention so they know when they can type. The called party begins typing and ends with two stars, like this **. Then the caller knows he can type and also indicates the end with two stars. When a party is ready to hang up the phone he writes four stars.
> When a party is ready to hang up the phone he writes four stars.
I wish we had a convention like this for text messages. Some generally accepted way to “hang up” that isn’t taken as rude.
It’s a nonissue with people you text frequently, the conversation just waxes and wanes naturally. Maybe it’s just me, but for texts with acquaintances, distant relations, etc, theres no good way to end the interaction like there is over the phone. You can’t just text “alright I gotta go, talk to you later”.
- 110 baud instead of 300 baud
- not full duplex
- carrier tone
I experimented with a Java application and FFT to try to write a soft modem, so I still know the exact specification by heart. Bit 1 was 960 Hz, Bit 0 was 1160 Hz, the carrier tone 1060 Hz, and there were 2 stop bits. This means, the teletype could transmit 11 letters a second.
The carrier tone is special: if someone stopped typing, the teletype switched to the carrier tone and kept it on for about 3 seconds then stopped.
Being not full-duplex Deaf users used a convention so they know when they can type. The called party begins typing and ends with two stars, like this **. Then the caller knows he can type and also indicates the end with two stars. When a party is ready to hang up the phone he writes four stars.
This is what my model (Telescrit) looked like: https://db1.rehadat.de/rehadat/bilder/TC058000/tc058773.jpg