Trunking system controller setup question

Post by **batdude** » Mon Nov 03, 2003 4:56 pm

i have two systems, both are type II.

One is UHF, 410Mhz, Smartnet OBT serial #001. Yep - 001. This is a 10ch system with MSF5k repeaters.

the other is a newer 800 system, most likely Smartworks and uses MTR2000 repeaters.

both of these systems exhibit behavior that i thought was impossible with a trunking system --- it's possible for subscriber units to "walk over" other people in the middle of transmissions.

i always thought it impossible for the central controller to issue a channel grant when a given talkgroup was already keyed up with a user?

is there a setting somewhere that's screwy here?

obviously - the difference in age between these two systems is immense - about 5 years difference... the OBT 400 meg system was put in during late 1988/early 1989... the other during 1997/8 or so.

anyone?

doug

Twisted_Pear · Post by **Twisted_Pear** » Mon Nov 03, 2003 8:32 pm

Set the subscribers to PTT-ID. You didn't say if they are or not.

Since the voice channel is active the controller has no control of who is allowed to talk since all the subscriber radio knows is to transmit on the voice channel input when the PTT is pressed (transmission or message trunking). If you make it have to contact the controller first (with PTT-ID), the controller should say, "no, bad user, call in progress."

-Wayne

800mhz radio · Post by **800mhz radio** » Tue Nov 04, 2003 6:46 am

Hi it is happening because your controler is set up for message trunking along with your mobiles there are two types of setup
transmission and message look at your as built for your central it
will show how it is set up.

RKG · Post by **RKG** » Tue Nov 04, 2003 8:46 am

To expand: with message trunking:

When the mobile issues a "disconnect tone" the controller leaves the voice channel up for a timer period. Any unit can talk over the voice channel repeater by simply sending voice in on the voice channel input freq with the connect tone (which restarts the timer); mobiles are programmed so that, if keyed during the timer runout, they xmit on the voice channel input, not the data input, and they send straight voice. And, a unit can talk over another unit: not a design feature, but a result of having the voice channel operate as a conventional repeater.

With PTT trunking:

When the mobile issues a disconnect tone, the controller immediately takes the voice channel down. All mobiles are programmed so that, when keyed, they send an ISW over the data input freq. One result is that a mobile can't key over another mobile, since he won't be xmitting on the voice channel input freq.

Message trunking is common for smaller systems with single sites or multicast sites. It saves a bit of wear and tear on the repeater and controller. PTT trunking is required for SmartZone systems, where the voice channel in use in various "zones" will not be the same.

Post by **wavetar** » Tue Nov 04, 2003 12:40 pm

To expand a tad further, the "PTT Trunking" RKG referred to & described is actually called "Transmission Trunking". You can set your radio to that & the walkover problems should go away, however the system won't let you access the current repeater during it's 'hang-time' either, since you are requesting a new voice channel everytime you key. If the radios you are using are capable of it, choose "PTT-ID Trunking", or "Wireline PTT-ID Trunking". The difference is it still allows hangtime like Message Trunking, for continuous conversations without re-aquiring a voice channel, while also eliminating walkover, since units are required to give their ID to the central controller on the control channel, even during regular voice conversations, including the hangtime. This is the trunking mode required for SmartZone systems.

Todd

larrybl · Post by **larrybl** » Wed Nov 05, 2003 2:52 pm

I hate to confuse the issue, but I have a smartnet system, and we are set up as message trunking with PTT ID set in all suscriber units. I also have a problem with folks stepping on one another. We do not wish to use Transmission trunking. Are you saying that PTT ID on Message trunking should prevent this?

Post by **batdude** » Wed Nov 05, 2003 3:00 pm

i have been waiting to respond to this

but you guys are WRONG

PTT ID did NOT fix this problem on either system.

next please

doug

Post by **wavetar** » Wed Nov 05, 2003 3:19 pm

What model radios do you have, and exactly what RSS screen are you choosing PTT-ID in? When we're talking about PTT-ID Trunking, we are not referring to turning on the function which would show the incoming user's radio ID, in case that's causing the confusion.

It should solve the issue, I know it works this way in both our SmartNet AMSS & SmartZone systems. It's the reason the third trunking option was created. Type I & II Privacy Plus systems did not have this option, but SmartNet did. Double-check the controller 'As-Blown' to confirm it really is a Smartnet system, as opposed to a Type II Privacy Plus system. Perhaps the Central Controller codeplug must be ordered as PTT-ID Trunking as well? I know you can choose between Message & Transmission Trunked when you order the controller, not sure about the PTT-ID.

Todd

apco25 · Post by **apco25** » Wed Nov 05, 2003 4:24 pm

for what its worth the two Type II smartnet systems I use both have this problem. Both are 800 analog, both are setup for PTT-ID in the radios and the system and yet you can still walk on someone.

The EDACS system I use does tx inhibit radios so you don't have this problem.

larrybl · Post by **larrybl** » Thu Nov 06, 2003 5:51 am

CONTROLLER CODE PLUG INFO:

Smartzone [0= none, 1= D786] 0
Smartnet II/28
SYSTEM TRUNKING TYPE
transmission or message trunked (TRNKTYPE) [t / m] m
SUBSCRIBER OPTION BYTES
Push To Talk ID System (PTTSYS) [y / n] y

CPS INFO
ASTRO SABER & XTS 3000
VER R03.00.00

PTT ID SET in the: TRUNKING / PERSONALITY / AVANCED Screen.

I have re-verified that it is possible for a radio to walk on another radio on the same talkgroup.

Post by **wavetar** » Thu Nov 06, 2003 5:53 am

Larrybl, I have no idea why it doesn't work for you, all appears to be ok. Time to give Motorola a call, I guess.

Todd

larrybl · Post by **larrybl** » Thu Nov 06, 2003 5:59 am

This has been one of the small quirks of this system sence I have worked here. Most of the users follow proper radio procedures (monitor before TX) and have gotten used to this problem. I will talk with a FTR about this, but if it involved blowing a new CP, we will probally hold off, seing that we are planning on replaceing the current 6809 with a MTC3600 later next year.

Thanks for the information.

RKG · Post by **RKG** » Thu Nov 06, 2003 7:48 am

I note that the controller info says that "message" trunking (versus "transmission" trunking) is selected. This is what enables talkover, because the voice repeater is available to anyone who keys up with the connect tone until the hang timer has expired.

Please note that Wavetar's correction of my terminology is correct (I make this mistake whenever I do this from memory). What I think you folks want is "transmission trunking" (i.e., a new channel grant required for each segment of a conversation), provided that this is consistent with your other system requirements. Note that changing would require reprogramming by the system or site controller AND all of the portable and mobile equipment.

From a Motorola Programming Manual:

Conversation Type:

Message Trunked:

After the initiator dekeys the radio, the voice channel stays active (hangtime) so other members of the talkgroup can respond on the same channel. If a radio in the talkgroup transmits during another user's transmission, they will talk over the other transmission.

Transmission Trunked:

No hang time and no talk over. When a radio is dekeyed, the channel is immediately deallocated and reassigned. If a user tries to talk over an active channel, the radio will not key until the channel is clear.

PTT-ID:

PTT-ID systems are similar to Message converation type systems with hangtime and talkover, but it sends an ID code to the controller when PTT is pressed. After the ID transmission, the radio goes back to voice channel to talk to the other users.

So go back to my post, substitute "transmission trunking" for "PTT trunking," and the explanation is correct. My apologies for the misnomer. Simply going from "message trunking" to "PTT-ID" will not solve the talkover problem, because the mobile unit will transmit on the voice channel and talkover. Also note that both the mobile radios and the system or site controller must be set to the same conversation type.

Trunking system controller setup question

Trunking system controller setup question

well...