Smart PTT

[billy2047]

Hi all,

Could someone tell the difference between "Inhibit on correct NAC" and "Inhibit on Status Symbols" under Smart PTT?

We're operating on conventional P25 (both simplex and repeated) with different NACs. We're having issue with units walking over each other. We don't have this problem on trunking because radio would bonk the other who is trying to talk when someone is already talking.

Thanks all!

 

[hitechRadio]

Strait from the CPS Help, CPS Help is your friend.

Inhibit on Correct NAC
Prevents transmission while the radio is receiving a digital (ASTRO) voice call that has a matching Network Access Code (NAC) for the current channel (see Rx Network ID).

Inhibit on Status Symbols
Prevents transmission while receiving a digital (ASTRO) voice call and when the 'last-received' signal status bit recorded was either inbound busy or unknown.

Either one would solve your issue, I would use Correct NAC inhibit, as Inhibit on status seems to inhibit on any invalid (unknown) signal, even interference.

There is also a new feature for Conv. P25 called Talk Permit Tone under TX Options, it does not have anything to do with your issue above but i thought i would mention it.
It gives a similar experience to trunking, the radio must receive an ACK to transmit, thus be in range of the repeater. Since there is no squelch tail on digital like an analog repeater. the plus side, It gives the user and idea they infact did hit the repeater.
It is a new feature, so your results may very. But our testing so far has been good. It also gives the user a TPT tone they are use to on trunking.

 

[billy2047]

I wasn't sure what inbound busy or unknown mean and how would a radio know a channel is busy or unknown when it is operating on simplex P25?

 

[dickie757]

The channel contains information that is kind of like logic. If the frequency in the channel has activity, is it the correct emission? This could be analog, NXDN, DMR, P25, M17, etc. If the emission type is recognized as a valid type by the variables in the channel, then the next step is to check out NAC, then talkgroup. If any of those variables do NOT match up to channel info, the light is illuminated, but no audio is passed to the speaker.

While most channel programs include logic to inhibit transmissions while the light is on, programming can allow tx during a busy channel situation, as is your case. It could be intentional or oversight.