A maximum of 64 half-duplex lines could be attached.
2.
A single scanner could attach up to 96 ( 64 for the first scanner ) half-duplex lines.
3.
This would allow about 160 half-duplex lines running at a mean speed of 120 cycles per second ( cps ).
4.
Up to three expansion frames can be attached for a theoretical capacity of 352 half-duplex lines and two independent channel adapters.
5.
Alternatively sixteen half-duplex lines running at 1200 cps ( 9.6 kbit / s ) would be the theoretical limit.
6.
This would give a theoretical limit of a million cps ( eighty 9.6 kbit / s half-duplex lines ).
7.
In practice the limit was lower as a scanner with more than 48 half duplex lines could not support any 9.6 kbit / s lines.
8.
Some computer-based systems of the 1960s and 1970s required full-duplex facilities, even for half-duplex operation, since their poll-and-response schemes could not tolerate the slight delays in reversing the direction of transmission in a half-duplex line.
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