Concept:  The NHRC-3/M2 controllers allow the connection of the newer Com-Spec TS-64 CTCSS encoder/decoder.  From the factory, the controller can be configured to provide reverse burst if the logic is provided from the controller to the TS-64, but what if you only want the PL tone on the repeater transmitter when the receiver is active (PL during COS activity only)?

The solution is simple.  Since the logic input already exists (Transmit PTT Input) on the TS-64 to allow the keying of the CTCSS tone when this pin is grounded, all we need to do is provide a keyed ground signal when the COS (CAS) is active.

Explanation:  This modification eliminates the ability of the TS-64 from keying the transmitter through the controller as originally intended by NHRC.  The PTT interface jack JP4 is reconfigured to provide a switched ground to JP4 pin 2 to allow the TS-64 to operate as a keyed CTCSS encoder.  Reverse Burst is generated when the COS disappears (user unkeys) and since the repeater controller has hang time, no keying is needed from the TS-64 to the transmitter.  One of the jumpers added below restores the PTT line as if jumper connector JP4 was never modified and the jumper was installed.

Procedure:  Jack JP4 on the controller is rewired to supply a keyed ground to the orange lead (pin 8) on the TS-64.

1. Cut the circuit trace as marked with the X in the image below.
2. Add the two jumpers as shown.
3. Use at least 200 mS hang time on the repeater controller.

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