QMS 2425, Reference

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Direction refers to the direction of signal flow as viewed from the
printer.
„
Return denotes “twisted-pair return” and is to be connected at
signal-ground level. When wiring the interface, be sure to use a
twisted-pair cable for each signal and never fail to complete con-
nection on the return side. To prevent noise effectively, these
cables should be shielded and connected to the chassis of the
system unit and printer, respectively.
„
All interface conditions are based on Transistor-Transistor Logic
(TTL) level. Both the rise and fall times of each signal must be
less than 0.2 microseconds.
„
Data transfer must be carried out by recognizing the ACKNLG or
BUSY signal.
„
The cable must have an overall braided shield, Belden 8345 or
equivalent.
„
Connectors must have shielded housings. The overall shield must
be bonded to the shielded housings at both ends of the cable.