Most Radio Telemetry Monitor and Control Systems have geographic high and low spots interfering with signal transmission strength resulting in one or more repeaters within the system. A repeater (click to see pic) records and forwards messages both outbound and inbound and is equipped with an omni-directional antenna to allow it to communicate in all directions. A repeater may be a standalone unit without input / output (I/O) capability or it may be a remote terminal unit manufactured by DFA having I/O and repeater capability as part of the unit.
The above graphic is an example of a transmission using a repeater. The System Control Computer (SCC)
sends a message intended for RTU #3 to RTU #1 which then sends or repeats the message to RTU #3. RTU #3 replies back to
RTU #1 which retransmits the reply message to the SCC. In this example, RTU #1 is called the Repeater.
Within a Radio Telemetry System, a Repeater is used to relay the messages outbound and inbound on each communication path.
Up to 16 Repeaters may be on each communication path with up to 8 paths possible or a star burst pattern.
Two Repeater types exist: Store and Forward and Dual Frequency.
For systems utilizing dual frequency repeaters, (two radios), a Repeater Board (P/N 0592) may be added to a
Remote Terminal Unit (RTU) making it a combined RTU-Repeater. A Repeater is AC or DC powered and may be solar powered
if radio traffic flow is low.
Unless circumstances require a dedicated repeater site, the DFA RTU at an existing site can be used for a repeater site.
This way the only additional equipment required is an antenna change from a Yagi type to an Omni type antenna.
An Area Controller (A-RTU) is an RTU with a LCD display and keypad for operator interface that has been programmed to
operate without a System Control Computer (SCC). An Area Controller may have up to eight (8) RTUs under its control.
In the above graphic, RTU #1 could be an Area Controller if the SCC were not there.
Many small water and wastewater systems utilize Area Controllers without an SCC and upgrade to an SCC configuration
as the Utility grows. Or in some systems, Area Controllers control clusters of RTUs and only the Area Controllers
communicate with the SCC.