Sync/Async Short Range Modem
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Sync/Async Short Range Modem
- The SRM-8V, Async/Sync Short Range Modem, is used
for local data distribution, connecting full or half duplex Sync/Async
DTEs to computers over unconditioned 4-wire lines. SRM-8V operates at data
rates up to 38.4 kbps, and at distances up to 19 km (11.7 miles),
depending on wire gauge and data rate (see Table 1).
- SRM-8V performs diagnostic loops in compliance with
the ITU V.54 standard. Two V.54 loops are available:
analog loop (V.54 Loop 3) and
remote digital loop (V.54 Loop 2). These loops are activated by either a
3-position switch or by the DTE interface Circuit 141 (Pin 18) and Circuit
140 (Pin 21).
A TEST LED lights when any of the diagnostic loops are ON.
- Asynchronous transmission is provided by internal
conversion from Sync to Async, in compliance with the ITU V.22 bis
standard. Different Async formats are switch-selectable.
- In Synchronous mode, transmit timing can be
provided by three alternative sources:
- Internal oscillator
- External clock
- Loopback clock derived from the receive signal.
- The modem's carrier can be strapped for either
continuous operation (point-to-point application) or switched operation,
controlled by the RTS signal (multipoint application, or passing control
- DTE/DCE switch enables direct connection to DTE or
DCE equipment, eliminating the necessity for a cross cable.
Note: When SW2 is set to DTE, the ANA switch
(SW7-2) should be strapped to DIS.
- The low transmit level minimizes crosstalk onto
adjacent circuits within the same cable. Data is transmitted and received
at a balanced impedance, ensuring high immunity to circuit noise.
Additionally, SRM-8V is coupled to the line through isolation transformers
which protect against AC or DC overvoltages.
- SRM-8V can operate without a power supply, by using
ultra-low power from the standard V.24/RS-232 data and control signals.
When the DTE cannot provide the power required, SRM-8V's power consumption
can be significantly reduced by disabling the LEDs (strap-selectable).
- The line interface consists of two independent
connectors: one is a 5-screw terminal block, the other is a selectable
RJ-12 or RJ-45 connector (see Ordering).
- Five LED indicators are available to facilitate
diagnostics: Test, Data Carrier Detect, Transmit Data, Request to Send,
and Receive Data.
- Synchronous or Asynchronous
- Data rates up to 38.4 kbps
- V.54 diagnostics, including local and remote
- Full or half duplex for multipoint or
- Half duplex over 2-wires
- Internal, external or receive clock
- Controlled or continuous carrier
- DCE/DTE switches
- Isolation transformers
- No AC power required
- LED indicators
- Miniature, lightweight, easy to install
Synchronous/Asynchronous Short Range Modem
||Specify 25-pin connector
M for male
F for female
||Specify line interface:
RJ-12 for RJ-12 jack
RJ-45 for RJ-45 jack
(Default is Terminal Block)
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