In addition to the main RS232 data interface for the internal modem, there is also a 600 ohm balanced line interface for connection to an external modem if preferred.  The line output can also be used as an audio monitor of the channel.

The ART modem has completely separate transmit and receive sections which can both run simultaneously.  The unit can therefore be used in full duplex applications (using two frequencies) with data going in both directions at the same time.  Even when running half duplex, the separate transmit and receive oscillators allows very fast data turn-round as the oscillators do not need to change frequency between transmit and receive modes.

The receiver is a very low current, double conversion superheterodyne with an active balanced mixer for very good intermodulation performance. Careful attention to spurious response, adjacent channel and blocking performance makes the product ideal for crowded telemetry radio channels.

All key operating parameters can be easily set using the supplied configuration software.

The ART supports Store-&-Forward operation when used with MODBUS and selected other protocols.  This allows an ART to act as a repeater and pass messages on to more distant sites which cannot communicate directly with the master-station.

The ART has been specifically designed around low current circuitry to allow use on remote sites without limited power.

In addition to the inherent low power consumption of the design, the ART also incorporates a number of sleep modes which reduce the consumption to below 100µA.  Sleep mode can be controlled either by an external input or by an internal timing circuit.

Up to 80 channels to be pre-programmed into the ART and rapidly selected using the two front panel rotary switches.  The switches can be locked-out under software control and the radio programmed for a single frequency by the user if preferred.

The transmit power can be accurately set in 1dB steps under software control.

The serial interface includes all handshaking signals and conforms to the standard pin-out arrangement for RS232 connections.  This allows off-the-shelf cable assemblies to be used for connection to external equipment.  The modem can also be set for “Key-on-Data” operation and then only requires the Tx Data, Rx Data and Ground pins to be connected.

For old or non tolerant protocols, where the presence of a mute (squelch) tail may cause a problem at the end of a message, a simple packetisation option can be enabled using the configuration software.

At 9,600bps, an optional forward error corrector can be enabled.  This gives an improvement of around 3dB in the BER=10-3 error threshold.

The transmitter within the ART has a time-out timer which allows the maximum continuous transmission time to be set in order to prevent channel blocking due to a to fault in any connected equipment.

The ART features a dc output whose level is proportional to the incoming RF signal level.  This is useful for long term monitoring of radio paths and simplifies alignment of antennas.