Datacom 1200

2020-12-29 - Reading time: 12 minutes

This is a weird post. Another one of those random things I never set out to write. But for some reason I feel the need to document things when there's little solid information online. Seeing anything go down the memory hole depresses me, so the least I can do is keep something alive with what I find.

A Half-Second Rack Focus Shot

I was surfing some old TV commercials from the 70s and 80s, as one does.

Eventually I came across this old CKCO Canadian TV station promo from 1983 called "We're Bringing It Home To You" over on the wonderful Retrontario channel on YouTube.

The promo features a quick montage tour of all the hot new technology and crew behind the station you're currently enjoying.

One of the machines that brings you their quality content has a fancy rack focus effect very early in the clip, at the 3 second mark. It's on a keyboard with the label "Datacom 1200" across the top:

Once in a while I get mentally snagged by something like this.

I see a technology from the era I don't recognize and go on a little detour for a half-hour reading about it. (Imagine this behavior spread out over a lifetime and a lot of things about me begin to make a lot of sense.)

Anyway, this time around I couldn't find... well, anything. The entire search engine bandwidth for "Datacom 1200" in 2020 is devoted to a product from a Brazilian company named "Datacom" that sells a family of network hardware. And one of the lines features "1200" in the name.

Hey, it's almost 40 years later. Whatchewgonnado?

A Lead!

Actually, it's only partially true that I didn't find anything. I fibbed a smidge.

In fact, the first search result for "Datacom 1200" is an empty listing on an printer ink company's website. Among the various third-party ink replacements they provide, under their "Other" category, is the "Bell DataCom 1200". 🤔

Ahh! Indeed, searching "Bell DataCom" as a full brand name sent me on a little trip that included this ad from Bell Canada in a mid-October 1974 issue of The Ottawa Journal; presumably* two older models of Datacom, the 500 and 600.

_{(*I say 'presumably' because the Amiga 500 came out after the Amiga 1000; numerical
superiority is not always an indicator of temporal positioning! 😉)}

 

The Bell Datacom is a line of old school printer terminals from the Bell Canada's "Computer Communications Group".

Pretty much what I expected. No real surprise there.

"The Datacom 500 terminal is a compact, self-contained and quiet unit that allows office personnel to send and receive messages from a remote computer. It is ideally suited for consumer-finance applications and such transactions as journal entries, payment inquiries and file up-dating."

"The Datacom 600 is a buffered keyboard teleprinter. This general purpose unit is useful in a wide variety of applications such as accounting information processing, order entry and invoicing, and inventory control."

A Quick Zenith 33000 Detour

One interesting, apparently unrelated thing to note: "For more information, just dial Operator and ask for Zenith 33000."

My first thought: maybe these Bell-branded terminals are actually sourced from a Zenith supplier and rebranded. Zenith, after all, dipped their toe into the computer world for a minute there, around that time.

But here's the thing: do a search for "Zenith 33000". You'll find a lot of old newspapers returning results (from various sites that want you to subscribe to all of them to get access to a single article... good luck on that).

And it's not limited to Bell, or even this line of terminals:

• "Increased sales... increased production... better inventory control... CCG helped Crossley Karastan Carpet Mills Ltd. achieve this, and more. Call us at Zenith 33000 today, if you too would like the red carpet treatment" -- Canadian Datasystems (Apr 1981)
• "TRANS-CANADA TELEPHONE SYSTEM 10020 Edmonton Call Long Distance (No Toll Charge) & ask for..zenith 33000"

This, however, is a dead end.

"Zenith 33000" is a Zenith number. Turns out this was a system of toll-free calling prior to modern toll-free numbers.

A fun bit of telephony trivia, to be sure, but it's completely unrelated to anything here. 😏

Back to the Datacom 1200...

A December 18th issue of Computerworld from 1978 refers to the 1200 model specifically, on it's introduction:

"The Datacom 1200 family of teleprinters has been introduced by the Computer Communications Group (CCG). Available as a receive-only (RO) terminal or equipped with a keyboard, Datacom 1200 prints bidirectionally at a maximum speed of 180 char./sec and produces up to 132 char./line.

Vucom Output

"Supplied by Digital Equipment Corp., the Datacom 1200 receive-only teleprinter can serve as a hard-copy output device for the Vucom 1, 3 and 4 series of CRTs, as a peripheral printer for mini- and microcomputer systems and for remote multicopy printing from a host data base in a stand-alone configuration.

"Rates for the Datacom 1200 in Canada are $2,715 for the RO model, with an additional $150 for the keyboard send-receive version. Filed rental rates, which are subject to regulatory approval, are $146/mo for the RO model, with an additional $7/mo for the KSR unit. Maintenance costs $44/mo.

Supplied by DEC, huh? Now that's interesting. From 1970 to the 80s, the once mighty Digital offered their famous DecWriter series of line terminals.

And I'm gonna call it now: the Bell Datacom 1200 is probably a rebranded DecWriter III.

I can't find anything specifically saying so, but I will make my case, and let you decide!

The Evidence

• The DecWriter III was released in January 1977. The Computerworld article is from December 1976, referring to January '77 availability for the Datacom 1200.
• Both have 180 cps printing speeds.
• Both support 132-characters per line, max
• The DecWriter III was a 1200 baud terminal; likely where the "Datacom 1200" number comes from.

But here's my smoking gun...

The keyboard of the DecWriter III compared to the corner of the Datacom 1200 we're seeing in the promo spot:

• Same shape Shift and Return key (though these are probably common for the era).
• Return has a pipe/backslash and a delete key to the right of it.
• There's a cluster of at least four keys above the -/+/~/backspace keys.
• There's even a bit of space for the custom Datacom 1200 badge.
• Oh, and they're basically the same color. 😏

I feel good about this. The evidence is pretty convincing. There's just not any official word I'm finding. Yet.

If you find anything, or know first-hand, hit me on Twitter and I'll update this post.

Still Remembered. Sort of.

One super interesting thing about "Bell Datacom" is that it shows up in a LOT of ink supplier listings -- the 1200 model, specifically. In fact, ink listings take up most of the "Bell Datacom 1200" search results on Google.

Even Staples seems to have an atrophied entry for it in their ink category. Guessing there's a lot of copy/pasting of "machines that use ink" among companies, and either the 1200 still gets play today (unlikely considering how little direct information there is on it), or it simply never got culled over the years.

Anyway...

This was a hell of thing to write based on a half second blip.

I just wanted this to be little more than an "I SEE YOU, DATACOM 1200" type post for anyone in the future who might look for it, and be confused by the lack of information. I didn't expect to do a full on bit of research, and even come to a reasonable conclusion about it. Huh.

Until next time. 🍻

BYTE's Audio Cassette Standards Symposium

2020-12-20 - Reading time: 11 minutes

(This is a mirror from swtpc.org [archive.org], which itself is a mirror from BYTE Magazine. Minor formatting changes have been introduced.)

BYTE's Audio Cassette Standards Symposium
Written by Manfred and Virgina Peschke
BYTE, Feb 1976, Pages 72 and 73

BYTE Magazine sponsored a symposium on November 7 and 8, 1975 in Kansas City MO regarding the interchange of data on inexpensive consumer quality audio cassette drives.

These drives may be used as one of the mass storage devices in the first generation of personal computers, and will retain importance for some time to come as a means of interchange of software between computer enthusiasts who purchase products of the small systems industry.

In order to promote the growth of the industry, BYTE sought to achieve an industry standard on audio cassette data interchange through a working conference.

We extend our greatest appreciation to the 18 people who worked very hard until late Friday night and Saturday morning to discuss the multitude of problems and solutions associated with digital recording on auto cassettes. The names of the participants are listed in Table 1.

In spite of the short time available, the participants were able to draft a set of provisional standards which seems to promise great reliability and is rather inexpensive to implement; implementations may be entirely in hardware, or may require a mix of software and some minimal hardware.

Considerations were given to the problems of speed variation among recorders and playback equipment, start and stop delays, recording density (or speed) versus reliability, and recording frequencies to avoid interference with the telephone network in case some users plan to transmit the tones of the cassette over the phone lines.

On Saturday afternoon, Mr. Felsenstein and Mr. Mauch volunteered to write up the consensus among the participants as to a provisional standard which has been reproduced below.

Provisional Audio Cassette Data Interchange Standard
The consensus among the participants of the audio cassette standards symposium at Kansas City MO sponsored by BYTE Magazine is as follows:

• The proposed standard centers around the use of a frequency shift modulation method from which serial clock data can be extracted at rates of up to 300 baud. The system is intended to be used with low to medium cost cassette recorders incorporating electrical stop and start capability which may be operated under program control.
• The technique proposed provides for long and short term tape speed variation, limitations in bandwidth due to effects such as tape misalignment, and the necessity to retain low cost and low complexity of the hardware. The technique allows for potential operation at higher tape speed than the nominal 1.875 inch/s (4.75 cm/s).
• A mark (logical one) bit consists of eight cycles at a frequency of 2400 Hz.
• A space (logical zero) bit consists of four cycles at a frequency of 1200 Hz.
• A recorded character consists of a space as a start bit, eight data bits, and two or more marks as stop bits.
• The interval between characters consists of an unspecified amount of time at the mark frequency. In this respect the data format is similar to that of asynchronous data communication.
• The eight data bits are organized least significant bit first, most significant bit last, and followed (optionally) by a parity bit. The total number of significant bits and the parity bit cannot exceed 8.
• Where less than eight data bits are used, the unused bits (following the optional parity bit) at the end of the character are mark bits (2400 Hz).
• Data will be organized in blocks of arbitrary and optionally variable length, preceded by a minimum of five seconds of marks. To avoid errors due to splice and wrinkle problems common at the beginning of tape, the beginning of the first data block will occur no sooner than 30 seconds from the beginning of clear leader.
• The contents of the data block are not specified.
• The data block ends after the stop bits of the final character.
• Bit clocking information may be extracted from the recorded waveform, which is always an integer multiple of the bit rate, regardless of tape speed. This permits the recovery and retiming of data by means of a UART, which requires a clock of sixteen times the bit rate, although other simple circuitry may be used.
• A reliable bandwidth of 3000 Hz was assumed in choosing mark and space frequencies due to the head misalignment expected between various cassette recorders. The recording technique is a redundant form of Manchester or bifrequency code which has a long history of reliability in the computer industry. In its present form it was proposed by three independent manufacturers at the conference. One cited reliability rates of one error in 10**7 characters for 200 passes.

Table 1: Participants at Audio Cassette Symposium.

Ray Borrill	1218 Prairie Dr, Bloomington IN
Hal Chamberlin	The Computer Hobbyist, P 0 Box 5985, Raleigh NC 27607
Tom Durston	MITS, 6328 Linn NE, Albuquerque NM
Lee Felsenstein	LGC Engineering, 1807 Delaware St, Berkeley CA 94703
Joe Frappier	Mikra-D, 32 Maple St, Bellingham MA
Bill Gates	MITS
Gary Kay	Southwest Technical Products Corp, 219 W Rhapsody, San Antonio TX 78216
Bob Marsh	Processor Technology, 2465 Fourth St, Berkeley CA 94710
Harold A Mauch	Pronetics, 4021 Windsor, Garland TX 75042
Bob Nelson	PCM, San Ramon CA
George Perrine	HAL Communications Corp, Box 365, Urbana IL 61801
Ed Roberts	MITS
Richard Smith	The Computer Hobbyist, P 0 Box 5882, Raleigh NC 27607
Les Solomon	Popular Electronics, 1 Park Av, New York NY 10016
Michael Stolowitz	Godbout Electronics, Box 2355, Oakland Airport CA 94614
Paul Tucker	HAL Communications Corp
Mike Wise	Sphere, 791 S 500 W, Bountiful UT 84010
Bob Zaller	MITS