RAD SRM-5SC,SRM-6SC Sync Multipoint Short Range Modems  

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RAD SRM-5SC,SRM-6SC Sync Multipoint Short Range Modems  


The SRM-5SC and SRM-6SC, Synchronous Short Range Modems, are used for local data distribution, connecting full or half duplex synchronous DTEs or controllers to computers. A pair of modems ensures integrity of data transmission over unconditioned 4-wire dedicated lines, for distances up to 14.5 km (9.1 miles), depending on the wire gauge and data rate
  • SRM-5SC and SRM-6SC are fully compatible and offer the same features. SRM-5SC is the smaller version, only 61 mm (2.4 in) by 18 mm (0.7 in); SRM-6SC is 110 mm (4.3 in) by 22 mm (0.9 in).
  • Transmit timing can be provided by three alternative sources:
    - Internal oscillator
    - External clock from the DTE, via pin 24
    - Loopback clock derived from the receive signal.
  • The carrier can be strapped for either continuous operation (point-to-point applications) or for switched operation, controlled by the RTS signal (multipoint applications). The LED indicator lights upon Carrier Detect (SRM-5SC only).
  • Innovative circuitry allows the SRM-5SC and SRM-6SC to operate without connection to the mains supply, by using ultra-low power from the data and control signals.
  • 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.
  • Coupling to the dedicated line is through isolation transformers which, in conjunction with other circuitry, protect against AC or DC overvoltages. The transformers are rated at over 1,500 VRMS, enabling connection of the modems to the local circuits provided by most national telephone administrations (P.T.T.s).
  • The line interface of SRM-6SC is a 5-screw terminal block. Optionally, the modem can be ordered with an RJ-11 or RJ-45 jacket or RJ-45 plug on 2m (6 ft) cable (via the terminal block). With SRM-5SC, the line interface is a 5-screw terminal block and choice of an RJ-11 or RJ-45 connector (see Ordering).
  • SRM-5SC and SRM-6SC are also available in a card version for mounting in the CMN-16 modem rack. For further information, refer to the CMN-16 and CMN-C6SC Data Sheets.


  • Transmission data rates up to 19.2 kbps, synchronous
  • Full or half duplex, point-to-point or multipoint
  • Internal or external clock
  • Transmission range up to 14.5 km (9.1 miles)
  • Transformer isolated
  • No AC power required
  • Easy to install
  • Compact, lightweight
  • LED indicator (SRM-5SC only)

Synchronous Modem (Sub-miniature)

Synchronous Modem (Miniature)

* Specify:
F for female 25-pin connector
M for male 25-pin connector
+ Specify line interface for SRM-5SC:
(In addition to terminal block)
RJ-11 for integral RJ-11 jack
RJ-45 for integral RJ-45 jack
# Specify line interface for SRM-6SC:
(Default is terminal block)
RJ-11 for RJ-11 jack
RJ-45 for RJ-45 plug on a 2m (6 ft) cable.
RJ-45S for RJ-45 jacket

For ordering information on the card version for the CMN-16 rack, see the CMN-C6SC Data Sheet.





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