RAD SRM-8V Sync/Async Short Range Modem

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RAD SRM-8V 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 signals end-to-end).
  • 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 loopbacks
  • Full or half duplex for multipoint or point-to-point
  • 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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