Re: Very Early Modems

> However, in the 1950s, IBM developed card-to-card directly without

>> paper tape and "over AT&T lines". Modems were developed to take good >> advtg of the available bandwidth (about 1200 baud). Undoubtedly the >> equipment and implementation was developed in close cooperation with >> AT&T. > This was the IBM "Card-to-card" transceiver. I don't know when they > first came out, but the Army started implementing them in a nationwide > network in September of 1956.

I saw one in operation between the GE Lynn Mass facility and somewhere else in 1960 or 61, in the same room as the 704.

I believe they used 4-wire leased lines, with data access arrangement > boxes provided by Ma Bell. So the signals going into the big grey box > next to the reader/punch were analogue. I don't recall what the > transmission rate was, but they sent EBCDIC directly without any > translation to a 5-channel code and no added headers.

No, it would NOT have been EBCDIC, which didn't emerge until System/360 around 1965. Try BCD or maybe some 2 out of 12 code.

Julian Thomas: ID=jt domain=jt-mj period net

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Julian Thomas
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