The Remote Telemetry Unit is an intelligent outstation which provides analogue and status data acquisition, and remote command execution. It can also be programmed to perform data reduction. data storage, reporting by exception or at preset time intervals, and to initiate control actions in response to local events independently of a Master Station.

Completely self contained, the RTU provides within a single environmentally sealed enclosure, plant interfaces, multiplexing control, intelligence, modem, and radio transceiver. Only an antenna and battery or mains power supply need be added.

The offshore version illustrated is designed for long periods of unattended operation in relatively inaccessible splash zone locations. It is also approved (Ex 'N') for operation in areas in which flammable or explosive gases may be present. Its extremely low power consumption permits this unit to operate from a compact battery pack with periods of up to 6 months between recharge or replacement.

The offshore RTU is provided with a front test panel which permits a check of both RTU and incoming plant signals without unsealing the unit. The case, front panel and controls are 'O' ring sealed and manufactured to military standards. All connections to the RTU are by sealed plug and sockets, permitting quick field replacement and the small size of the unit allows hand carriage to a suitable service environment. A screw in breathing desiccant-dehumidifier is fitted which maintains a dry atmosphere within the RTU in 100% humidity environments whilst also providing pressure equalization to compensate for external temperature and pressure fluctuations.

The Base Station acts as communications controller and operator interface. It uses the same electronic modules as the RTU plus a range of plug-in operator interface modules which provide analogue and digital displays, alarm enunciators, control and status functions. Keyswitches on the power supply, command, and alarm trip level adjust modules permit three levels of access to the system.

A feature of the system is a high degree of self monitoring. The health of Remote Stations can be monitored automatically by the Base Station which raises alarms if faults are detected. Also the selectable display enables engineers to access and display test voltages from any RTU without leaving the control room.

On larger systems, this unit functions as a front end communications controller and back-up emergency control position for colour graphics, visual display monitors, keyboards and printers, supported by a PDP11/23 mini computer or similair.

Base Station colour graphics terminals use a high level interactive language which enables plant mimic diagrams to be rapidly developed, and easily altered on site to reflect changes in plant configuration. Three levels of access are available, protected by passwords, for operators, maintenance engineers, and software engineers.

Special purpose keyboards with keyswitch protected areas provide a simple, clear operator interface requiring a minimum of user training.

The integral radio permits these units to access any RTU from a field location and obtain a status report or transmit command signals for example an emergency shut down signal.

These units act as a back-up to the Base Station, and a useful field test unit. Features include:

Receive and display analogue and status data

Command transmission

Waterproof alloy or Kevlar case options

Audible and visual alarms on analogues

30 hour rechargeable battery

Anti-shock mounted electronics

Optional chart recorder