MTR 2000 and JPS Voter Interfacing (need active High)

[joelhorton]

I have installed a JPS Voter system with three voter receiver sites with audio tied back to the JPS comparitor and connected to a MTR 2000 transceiver.

The problem is the interfacing of the audio to the wireline black connector on the back of the MTR 2000 (a receiver site and the sole VHF conventional transmitter site) and the active low connection to the green connector.

I have the system working as a active low, which means that the JPS voter sends a +5VDC to the MTR 2000 all the time and the voltage goes to zero volts when the JPS routes transmit audio to the transmiter.

How can I get the MTR to accept an active high which is programable from the JPS?

The reason for the active high request is that if the JPS goes down: in the current active low state the MTR 2000 stays keyed up all the time. The prefered solution would be to have a failsafe condition that results, when the JPS voter is down or off, the MTR 2000 falls back to a single site transceiver.

[Will]

You need an open collector output from the voter. It still would be active low to key the MTR.

[wavetar]

Will's suggestion will work if the voter has an open collector (ie: not ground) output. Or build a simple transistor switching circuit which would apply the ground whenever the +5v from the JPS is present.

Todd

[psapengineer]

Maybe this will help.

Here's the traditional approach that has been used since the times of MICOR:

The JPS voter can, if I recall correctly, produce Tone Remote Keying.

Normally the 4 Wire audio could be used on the MTR2000. The MTR2000 "Spectra-Tac" Rx audio is connected to a SVM module. The output of the JPS with TRC is connected to the MTR2000 Tx 4W audio.

Keying prioroty in the MTR2000 is set to lowest priority = internal repeat, medium priority = TRC.

Then, if the JPS fails, the keying priority reverts to in "station" repeat.

This mode may also get the Tx on the air faster since it's internal repeat with start the keying process if the co-located Rx hears the signal.


Lastly, and more in line with your question, we had a similar challenge when interfacing our simiulcast system. We needed to have the JPS voter drive the -48V E&M keying. We chose to add a pilot relay (Potter Brumfield R10 12V 4PDT biforcated silver) and let a real live contact do the work. I'm recalling that we used the "unsqulched" indicate summary output for faster PTT and set the DIP switch to "fail" the module on loss of audio and status tone.

Good Luck, Bob