Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!cs.utexas.edu!wuarchive!gem.mps.ohio-state.edu!apple!sun-barr!texsun!texbell!vector!telecom-gateway From: tanner@ki4pv.uucp (Dr. T. Andrews) Newsgroups: comp.dcom.telecom Subject: Re: The 'Public Telegraph Office' Message-ID:Date: 23 Sep 89 12:01:45 GMT Sender: news@vector.Dallas.TX.US Organization: CompuData, Inc. (DeLand) Lines: 33 Approved: telecom-request@vector.dallas.tx.us X-Submissions-To: telecom@eecs.nwu.edu X-Administrivia-To: telecom-request@vector.dallas.tx.us X-TELECOM-Digest: volume 9, issue 402, message 2 of 11 ) ... you mentioned that the [baudot tty] speed ) was around 60 baud. Well, it was actually something called "75-speed" ) which indicated a maximum speed of 75 WPM, transmitted in 5-level ) "baudot" encoding. Some of these 5-level devices could actually be geared for different speeds. The most common speed for the units, if you find them today, is 45.45 baud (with 1.5 stop bits!), which works out to ~6 chars/sec (commonly called 60 WPM). ) Actually, they used a "switch" character to flip-flop between ) meanings of particular bit patterns. They used two characters. There was a "shift" character (sometimes called "figs", bit pattern 0b11111) which forced the second character set. To drop back to letters, the "unshift" character (sometimes called "ltrs", bit pattern 0b11011) was sent. As a user-settable option, the machine could also be set to "unshift-on-space", which meant that if a space (0b00100) was received when the machine wsa in shift mode, it would drop back into unshift mode. The user selection of the "unshift-on-space" option is made by moving a metal bar under the vanes. I do mean "drop" - shift mode was handled by raising the carriage so that the other row on the type slugs would hit the platen. The "unshift" got a nice gravity assist, and made a nice sound. Those old model 15 and model 19 teletypes were fascinating to watch. ...!bikini.cis.ufl.edu!ki4pv!tanner ...!bpa!cdin-1!ki4pv!tanner or... {allegra attctc gatech!uflorida uunet!cdin-1}!ki4pv!tanner