DIGITAC voting unit

[engineer]

I have an 8 channel digitac voter which is also fitted with one TX card as it was formally used in a voting, rebroadcast station (trunk)

I wish to use it as a receiver only voting system where no signal RSSI encoding is used. Ie I wish to vote best signal from signal to noise measurement using none Motorola radio sets.

The simple question is, will the Digitac do this when re-configured in software ?

I have a personality programming manual for the unit, plus an installation manual.. When I power up the unit, after self test I get fail lights on each RX channel. I presume this is because a signal expected at the rx port is missing ? note I have not changed the personality settings from the original system.

If I apply audio to each RX channel (1Khz at -10dBm), the fail light remains on and no voting takes place. If I force the channel to vote by use of the toggle switch, then I get audio out on CH3 O/p 1Khz -10dBm.

The reason for the simple question above is to save lots of time programming and trying to get the unit to do something it is not designed to do.

Thanks for any help
Joe. U.K.

[engineer]

Answer received by private mail.
As suspected a channel tone which is present whilst the receiver is inactive sets the channel ready to vote. Incoming RX audio is voted as the tone is removed by mute detection at the receiver.

many thanks to Keith. here is a copy of returned mail.
Thanks for the information Keith, I did note in the manual tones were spoken of but not specifically in the RX role. I guess it is a kind of line-fail detection.

We normally use a system which requires a small card to be fitted into the receiver. The card encodes the RSSI value into a step tone and the through audio is notched so as no inter-reaction between audio and inserted tone takes place. The voter simply looks for the highest tone (best RSSI) neglecting of course link quality.

I was hoping the digitac just voted from signal to noise, and I did not have to get involved with adding stuff to the receivers which by the way are MCS2000 located in parts of the city where inbound reception is poor from.


Once again, many thanks for your time and consideration.

Joe Bell G4PMY

[Bill_G]

Joe - Unfortunately it is a holiday in the US. So I do not have the manuals in front of me to give you the pinouts to the two system plugs. The Digitac is an analog S/N voting comparator that can handle (if I recall correctly) up to eight rcvrs (two cards by four rcvrs each), and one transmitter. All connections are done in the back on the two 25pr connectors - one is the audio, the other is the i/o and alarm. In a Motorola system the rcvrs send status tone during standby (not receiving). Status tone is 2175hz at 13db down from the expected rx level generally injected into the comparator in the -20db range. Rx is expected in the -10db range. Upon carrier det, the rcvr status tone mutes. Loss of status tone by the comparator is assumed to indicate carrier det, and the S/N voting process begins. The base station is keyed using Moto standard tone control, and the voted audio is routed to the station xmit, and to the console rx line. The console tx input has priority / supervision over the xmit audio. The comparator will remain keyed until either (a) all enabled rcvr inputs have status tone present, or (b) the comparator times out according to a programmable variable. If an input times out, the fail light will remain on until status tone is present.

[Bill_G]

Joe - It sounds like you're using Dalman / Simoco radios. If you can pass E&M, you can trick the Digitac into working, You'll just need a local 2175 generator to qualify the tone det in each rcvr channel.