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Ibm 2780

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Subject: IBM System/360, Computer terminal, Binary Synchronous Communications, Basic telecommunications access method, Anthony James Barr, Data 100
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Ibm 2780

The IBM 2780[1] and the IBM 3780[2] were devices developed by IBM to perform Remote Job Entry (RJE) functions. They communicated with the mainframe via Binary Synchronous Communications (BSC or Bisync).

2780

The 2780, first shipped in 1967,[3] came in four models. The Model 1 could read punched cards and transmit the data to a remote host computer, and receive and print data sent by the host. The Model 2 added the ability to punch card data received from the host, The Model 3 could only print data received from the host, but not send data. The model 4 could read and punch card data, but had no printing capabilities.

The 2780 used a dedicated communication line at speeds of 1200, 2000, 2400 or 4800 bits per second. It was a half duplex device, although full duplex lines might be used with some increase of thruput. It could communicate in Transcode (a 6-bit code), 8-bit EBCDIC, or 7-bit ASCII.

The card reader/punch unit, similar to an IBM 1442, could read up to 400 cards per minute(cpm) and punch up to 355 cpm. The 2780 line printer was similar to the IBM 1443[4] and could print up to 240 lines per minute (lpm), or 300 using an extremely restricted character set. The 2780 was capable of local (offline) card to print operation.

3780

The IBM 3780, an enhanced version of the 2780, was announced in May 1972. [5] The 3780 was developed by IBM's Data Processing Division (DPD).[6]

The 3780 dropped Transcode support and incorporated several performance enhancements. It supported compression of blank fields in data using Run-length encoding. It provided the ability to interleave data between devices, introduced double buffering, and added support for the Wait-before-transmit ACKnowledgement (WACK) and Temporary Text Delay (TTD) Binary Synchronous control characters.[7]

The 3780 could read cards at 600 cards per minute and punch 160 columns per second. The printer was rated at 400 lines per minute.[8]

These devices were later emulated on various types of equipment, including eventually the personal computer. A notable early emulation was the DN60, by Digital Equipment Corporation in the late 1970s.[9]

2770, 3770

A similar device, the 2770, announced in 1969, "was said to surpass all other IBM terminals in the variety of available input-output devices."[10] The 2770 could attach the 2213 Printer, 2502 Card Reader, 545 Card Punch, 2265 Display Station, 1017 Paper Tape Reader, 1018 Paper Tape Punch, the 50 Magnetic Data Inscriber, and the 1255 Magnetic Character Reader. The printer and devices for any two other media could be attached to one 2772 Control Unit.[11] The 2770 was developed by the IBM General Products Division (GPD) in Rochester, MN.[12] An SNA successor, the 3770, a Data Processing Division (DPD) product, appeared in 1974.[13]

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References

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