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LIMITED-DISTANCE MODEM 56/64
The Modem’s carrier is strap-selectable for either
continuous operation, or switched operation for passing
control signals end-to-end. Switched operation is
controlled by the RTS signal.
The Modem performs diagnostic loops in compliance
with the ITU V.54 standard. Two V.54 loops are
available: local analog loop (V.54, loop 3) and remote
digital loop (V.54, loop 2). The loops are activated by a
3-position switch in all models or by the DTE interface
Circuit 141 (Pin 18) and Circuit 140 (Pin 21). The Test
LED lights when any diagnostic loop is active.
The low transmit level minimizes crosstalk onto
adjacent circuits within the same cable. Data is
transmitted and received using a balanced interface,
ensuring high immunity to circuit noise. And the
Modem is coupled to the dedicated line through
isolation transformers which, in conjunction with other
circuitry, protect against AC or DC overvoltages.
The line interface consists of two independent
connectors: a 5-screw terminal block, and a selectable
RJ-11 or RJ-45 connector.
