Talk:ASR-33 Teletype

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The teleprinter article says The 33 ASR was ubiquitous as a console device in the early minicomputer era.

How do you connect a ASR-33 to a minicomputer? --Abdull 06:45, 8 June 2007 (UTC)

Usually with a 20mA loop inteface, or was that a trick question :-) MarkMLl 22:42, 10 September 2007 (UTC)

I recall using an ASR33 in high school. It was in a classroom and had a handset cradle 110 baud modem. I do not recall the connection between the ASR33 and the modem. I do remember dialing the number, hearing the beep, and putting the handset in the cradle. We then connected to a Honeywell minicomputer running GCOS. I would guess the connection to the ASR33 was RS-232. Karstdiver 00:00, 29 July 2007 (UTC)

I've got a set of ASR manuals somewhere, can anybody comment on whether Teletype is sufficiently defunct that it would be permissible to include a scan to illustrate the internal complexity? MarkMLl 22:42, 10 September 2007 (UTC)

I'm no expert, but I date back to the says when both 20ma current loops and RS232 were common. Many DEC devices in the PDP11 era supported both. Anyway, if I remember correctly, the intended advantage of the current-loop interface is that a current loop is _much_ more resistant to electrical noise than is a simple voltage interface. This was more important ion the old days when a computer would span several equipment bays, and where a remote device might be separated by a goodly distance from the host, and almost certainly on a different electrical feed. I don't remember the details, but the operational distance limits on a 20 ma current loop (e.g. on an electrically noise factory floor) were much greater than RS232.

These details don't belong on this page, of course, but I do question the implication that computers had 20 ma interfaces merely because that was what an ASR33 used.

Steven M. Haflich (talk) 03:36, 19 March 2008 (UTC)