RAD SRM-3D Ultra-Miniature Async Short Range Modems 

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RAD SRM-3D Ultra-Miniature Async Short Range Modems 


The SRM-3D, ultra-miniature asynchronous Short Range Modem, is used for local data distribution, connecting full duplex asynchronous DTEs to computers. The SRM-3D ensures integrity of data transmission, using unconditioned 4-wire dedicated lines at data rates up to 19.2 kbps. It operates over distances up to 21 km (13 miles) depending on wire gauge and data rate

The SRM-3D connector is 9-pin D-type. This connector, as well as the ultra-miniature size of SRM-3D, make it an excellent choice for computers such as Unisys U6000/50 and U7000/52 or IBM PC/AT. SRM-3D is compatible with SRM-5D and SRM-6D, thus enabling connection of equipment using a 9-pin connector to equipment using a 25-pin connector

  • The low transmit level minimizes cross-talk onto adjacent circuits within the same cable. Data is transmitted and received at a balanced impedance, ensuring excellent immunity to circuit noise.
  • The modem incorporates innovative circuitry design, which enables the unit to operate without connection to the mains supply, by using ultra low power from the standard EIA RS-232-C/ITU V.24 data and control signal voltages. The modem operates fully even if only Transmit Data is connected (i.e. without the DTE sending Request to Send or Data Terminal Ready signals). Both positive and negative signals are generated in compliance with EIA RS-232-C/ITU V.24 standards, regardless of constantly low or constantly high Transmit Data.
  • The line side of the SRM-3D offers connection to the RS-232-C plug ground. This may be connected to the shield of the STP wiring to provide end-to-end ground continuity


  • Asynchronous transmission up to 19.2 kbps
  • Transmission range up to 21 km (13 miles)
  • Ultra-miniature modem using hybrid technology
  • No AC power required
  • 9-pin RS-232-C/V.24 connector
  • Compact, lightweight, easy to install
  • Plugs directly into IBM PC/AT and Unisys U6000/50, U7000/52
  • Can be used with both STP and UTP

Async modem

* Specify:
F for female 9-pin connector
M for male 9-pin connector
+ Specify line interface:
RJ-11 for RJ-11 jack
RJ-45 for RJ-45 jack (default is Terminal Block)




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