8
ASYNC SHM-NPR
The SHM-NPR features a DCE/DTE switch. This
allows it to operate as a DTE in order to connect to
another DCE, such as a multiplexor port, without
requiring a cross cable. The carrier can be strapped
for either continuous operation (point-to-point
applications) or for switched operation, controlled
by the RTS signal (multi-point applications). Delay
between RTS and CTS is strap-selectable to 1 or
12 msec.
The low transmit level minimizes crosstalk onto
adjacent circuits within the same cable. Data is
transmitted and received at a balanced impedance,
ensuring excellent immunity to circuit noise.
Additionally, the SHM-NPR is coupled to the
telephone line through isolation transformers
which, in conjunction with electronic circuitry,
protect against AC or DC overvoltages.
Innovative circuitry design allows the SHM-NPR
to operate without connection to the main supply,
by using ultra-low power from the standard EIA
RS-232/ITU V.24 data and control signals. To ensure
proper operation, the equipment connected to the
SHM-NPR should provide at least one of the
following signals: RTS (Circuit 105) or DTR
(Circuit 108.2).
