Bill_G wrote: ↑
Tue Dec 31, 2019 11:13 am
neonzx wrote: ↑
Tue Dec 31, 2019 9:29 am
Seen it. Or show them a Silent 700 and have them ask what those rubber cups are for. *hint, not drink holders
Now we're talkin! Those hearing impaired terminals were around for a very long time. Every 911 PSAP had one.
Not to nitpick excessively, but the Silent 700 wasn't a TDD device. It was a general-purpose computing device. Those of us who lived through this era of computing well recall the Silent 700. If you dreamed of mobile computing, this was your answer; you were really stylin' if you were important enough or cool enough to try to stay connected with this thing at 300 baud while you were out and about.
As I recall (a cousin is deaf-from-birth and had one) TDD's were a bit smaller and they used a different type of technology, such as a one-line LCD screen. They were a bit more portable (potentially battery operated) and if they had a printer, it was often smaller (more like a cash register receipt) than the Silent 700.
As I recall, I checked out connecting my cousin's TDD directly by phone to my printing terminal in the 70s, but that was not possible. TDD's weren't directly compatible with standard ASCII terminals like the one here, because they used a 5-bit encoding (basically the upper case alphabet and a couple other characters) to enable them to use a lower transmission speed on poor quality lines. Ascii was 7 or 8 bit plus optional parity bits, and could carry a much wider range of characters. The 300 baud couplers of the day, like the one on this unit, typically required a high-quality phone line. Damage to the wiring in the house or office that generated noise meant you couldn't reliably move data down the wire, and you'd see frequent connection drops, etc., at 300 baud. The TDD system, which was designed in the 1960s, didn't need high speed because it was only for personal messaging and not running business applications, but it needed the ability to connect on much noisier connections. Business applications required faster speeds as they were sending a lot more information to the user, and were able to require a higher-quality connection to do it.
Customer service centers supporting TDD users may have used general purpose equipment via a protocol converter for operator comfort and productivity, but I am quite certain that standard ASCII terminals such as the TI terminal here were not used by the users out in the field.