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| The Remote Terminal Unit (RTU) is a self-contained processor-controlled data gathering unit, operating from a –21 to –60 Vdc station battery. It is capable of monitoring up to 32 alarm points, controlling up to 16 remote control points and accepting up to 8 analog voltage inputs. The alarm point inputs may be activated in a variety of ways, |  |
| for example, relay contacts and transistor keying to ground or positive or negative battery. The RTU can output negative or positive voltage to be keyed by PNP or NPN transistor to ground. The polarity selection is by means of jumper straps in the RTU and selection is ganged in banks of 16 points. Therefore, an RTU with 32 alarms may have 16 points operated with negative and 16 points operated with positive polarity inputs. |
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All information contained within the RTU is maintained in nonvolatile RAM and may be accessed from the LCD for viewing. Editing or operation of relays is restricted as long as the RTU is in normal operation and under the Master Terminal’s control. Local operation and editing must obtain release from the Master Terminal and be Off-line. When the unit is returned on-line, the Master will recognize any and all changes and report the differences at the Master for operator intervention to either update the Master changes to either update the Master from the Remote or override the Remote changes from the Master. Front panel controls and 16 character by 2 line LCD display allow local operation of remote control functions, viewing and editing configuration of alarms and control points. The display will automatically page between the summarized page and individual alarms in banks of 16 points. Detailed configuration information, including point labels, are displayed on demand with FUNCTION, PAGE, and CURSOR KEYS. System Time and Date clock may also be viewed with the TIME key. System activity is summarized by three front panel LED lamps. An alarmed condition is indicated by a Red lamp. Communication with the Master is indicated by a Green lamp and communication errors or total failure is indicated by an Amber lamp. Errors flash the lamp and total failure turns the amber lamp on steady. The Green lamp is ON only for the duration that the RTU is in direct contact with the Master and OFF when the Master is in contact with other stations. |
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RS-232 electrical interface at 1200bps (can be set from 300bps to 38.4 Kbps) with built-in 3-port digital bridge. Ports 1 and 2 of the bridge are guarded with a relay operating in the fail-safe mode to bypass the station in case of total failure. |
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Ardax’s Analog ASK Modem operates at 1200bps over the baseband of analog radio equipment or VF multiplex equipment. |
| The RTU operates with its own monitoring program, independent of the Master Terminal. It continues to Time and Date stamp all events and logs the information in nonvolatile RAM. When called, these buffered events and logs are transmitted to the Master. It will continue logging information even if the Master Terminal is shutdown for long periods of time. Multiple events on any one or more points are held in a stack until the Master is back on-line and calls the RTU. When called, the RTU transmits all activities with their original Time/Date information to the Master. System history and sequence of events information is not lost due to Master Terminal shutdown/failure or Microwave outage. |
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