Applications of the RT9000 Radio Telephone


Payphone Operation with SPM (back to top)

The RT9000 can be configured for payphone operation with Subscriber Pulse Metering (SPM) by the addition of an optional integrated circuit. This renders the RT9000 completely transparent to SPM signals and line reversals. Both SPM pulses and line reversals are detected at the CO unit and are reproduced at the subscriber unit.

For payphone operation, the 12/16KHz SPM tones from the exchange are detected by the SPM decoder and translated by the microcontroller to FSK tones that are transmitted over the radio link. At the Subscriber side, after reception and detection of the FSK tones they are translated back to 12/16 kHz tones by the microcontroller and re-injected into the telephone line.

Payphone Operation with line reversal (back to top)

A line reversal at the exchange side is detected by a line polarity sensor and is transmitted as an FSK signal to the Subscriber unit which reproduces the line reversal by activating the line reversal relay



2-Wire Single Channel (back to top)
  • A basic system consists of one RT9000 unit connected to the nearest available 2-wire telephone line and one RT9000 unit connected to a regular rotary or touch-tone dial telephone set at the remote location, providing the user with normal full duplex telephone service.
  • The telephone interface has all the necessary capability such as off-hook or on-hook, dialling, ring detect and ring generate to permit automatic processing of incoming and outgoing calls, and is compatible with most telephone exchanges.
  • This configuration provides the subscriber with normal full duplex telephone service with all the necessary capability such as off-hook or on-hook, dialing, ring detect and ring generate to permit automatic processing of incoming and outgoing calls and is compatible with most telephone exchanges.
  • The CO unit detects ringing voltage and signals the subscriber unit to generate the same ringing voltage at the subscriber telephone. It also detects off-hook and dial pulse signals coming over the radio link in the form of 3825 Hz FSK. It converts these to signals to off-hook and dial conditions on the telephone line


    2-Wire 4-Line Concentrator (back to top)

    With the optional 4-line concentrator board mounted at the CO unit, up to four subscribers can share the same radio channel on a private-line basis. Each subscriber is connected to his own private line at the CO for automatic billing. The 4-line option offers full privacy to the subscriber by means of coded ringing and ensures that only the telephone being called will ring. Each subscriber unit has its own unique identification (ID) programmed during the initial software configuration.

    4-Wire E&M (back to top)

    The CO unit can be connected to the exchange via 4-wire E&M. To setup the RT9000 for 4-wire operation requires only the selection of appropriate DIP switches on the controller board.

    In this mode, the CO unit will ring the subscriber when it receives a ground on the 'E' lead instead of ring voltage as in the 2-wire operation. An 'off-hook' condition from the subscriber is signaled to the exchange by providing battery (or ground) on the 'M' lead. Dial pulses are also signaled by pulsing on the 'M' lead.

    4-Wire E&M Link Radio

    In this mode the radio functions strictly as a carrier operated, 4-wire E&M link radio without any FSK protocol. A ground on the ‘E’ lead will cause the radio to transmit and open the audio gates. On detecting a carrier, the squelch circuit (COR) will open and activate the E&M relay, which places a ground onto the ‘M’ lead. It will also open the audio gates.


    Repeater System (back to top)

    If the terrain is such that the SUB and C.O. locations are out of radio range, a considerable extension of range is obtained by employing a repeater.

    The repeater consists of two radio units connected back to back so that on detecting a carrier operated relay (COR) the receiver of one keys the transmitter of the other and vice versa. The back to back repeater can be configured by connecting two RT9000 radios together via the optional repeater cable.

    A total of four frequencies are required for repeater operation. F1/F2 between the C.O. and the local repeater and F3/F4 between the Subscriber radio and the repeater facing it. Directional antenna systems are employed and frequency allocation has to be chosen to provide sufficient isolation between the two units. To select the repeater function, see the option select switch table.

    Order wire operation (back to top)

    Two RT 9000 Subscribers can be connected to function as an order wire between two points. In this case both radios are configured as a Subscriber. If the handset is lifted in one location, a 3 second ring automatically takes place at the other Subscriber location. When both locations are off hook, normal two way conversation can take place. In the same fashion two fax machines could be connected together.

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