RAD Data Communications, Inc. Async/Sync 2-Wire Short Range Modem SRM-5SX

FEATURES

• SRM-5TX and SRM-6TX, Asynchronous 2-wire Short Range Modems, are used for local data distribution, connecting asynchronous V.24 digital equipment. The modems operate full duplex over existing 2-wire single twisted pairs or coax cables at data rates up to 19.2 kbps, over a range of 1 km (0.6 miles).

• SRM-5TX and SRM-6TX are fully compatible with each other and offer the same features. SRM-5TX is smaller, only 69 mm (2.7 in) by 18 mm (0.7 in); SRM-6TX is 110 mm (4.3 in) by 22 mm (0.9 in).

• SRM-5TX and SRM-6TX are also available as cards for mounting in a 19' modem rack (see the CMN-16 and CMN-C6TX data sheets).

• The transmit carrier is strap-selectable for either continuous operation or switched operation. The switched carrier operation enables transfer of one control signal end-to-end, making the modem suitable for connection to printers and statistical multiplexers. When in switched carrier operation, the carrier is controlled by the DTR signal (Circuit 108/2) and transferred to the DSR signal (Circuit 107) in the opposite modem. The DCD signal (Circuit 109) remains ON, regardless of the transmit carrier strapping. A LED indicator lights on SRM-5TX, whenever DSR is present.

• Innovative circuitry allows SRM-5TX and SRM-6TX to operate without connection to the mains supply, by using ultra-low power from the data and control signals.

• Coupling to the twisted pair line is done via isolation transformers which, in conjunction with other circuitry, protect against AC or DC overvoltages.

• The low transmit level of the modems minimizes crosstalk onto adjacent circuits within the same cable.

• The modems are available with a male or female integral 25-pin connector for the DTE interface, and a 3-screw (2-wire and ground) terminal block for the line. SRM-6TX is available with an RJ-11 connector, an RJ-45 connector or a female BNC on a pig-tail.SRM-5TX comes with a choice of RJ-12 or RJ-45 connector (see Ordering), in addition to the terminal block.

Note: RJ-12 is an RJ-11 connector with Pins 1 and 6 grounded.

FEATURES

SRM-5SX and SRM-6SX, Synchronous 2-wire Short Range Modems, are used for local data distribution, connecting full duplex synchronous terminals to computers. A pair of modems ensures integrity of data transmission over 2-wire dedicated lines, for distances up to 1.3 km (0.8 miles), depending on wire gauge and data rate.

• SRM-5SX and SRM-6SX are fully compatible and offer the same features. SRM-5SX is the ultraminiature version, only 61 mm (2.4 in) by 18 mm (0.7 in); SRM-6SX is 110 mm (4.3 in) by 22 mm (0.9 in).

• Transmit timing can be provided by an internal, external or loopback clock derived from the receive signal.

• Innovative circuitry allows SRM-5SX and SRM-6SX to operate without connection to the main supply, by using ultra low power from the data and control signals. For optimum operation, devices connected to SRM-5SX and SRM-6SX should provide RTS (Circuit 105) and DTR (Circuit 108.2) signals.

• The low transmit level minimizes crosstalk on adjacent circuits within the same cable. Data is transmitted and received using a balanced signal, 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 1500V RMS, enabling the connection of the modems to local circuits provided by most national telephone administrations (P.T.T.s).

• The line interface for SRM-5SX is a three-screw terminal block, and either an RJ-12 or an RJ-45 connector. The line interface for SRM-6SX is a three-screw terminal block, RJ-11 or RJ-45 connector. Optionally, SRM-6SX can be ordered with BNC female connector on a short cable (see Ordering).

Note: RJ-12 is a 6-pin RJ-11 connector with ground on pins 1 and 6.