type I/II i hybrid system Unknown ISW request

[icelander]

I have a Motorola type I/ type II i hybrid system with type 1 fleets as well as type II fleets active on the system. There are no type IIi users on the system.

when logging into the central controller I get the following quite often and usually about 2-3 pages listed.

central/status: main central, active
site: site 1
device name: central site controller
device number; 0E0
condition: error message
task number: 06
message: unknown ISW request. 37 6B = ID; 30 = call type

can anyone offer up any ideas as to why I keep getting these ISW error messages on the system. Some of my customers are telling me that they are also hearing other parties on their fleets as well as other divisions of their own company on other fleets they use.

any ideas

[portsmouth]

Hi Icelander.

A good one. We have a ten channel smartnet trunking system. We converted from type I to type II trunking a few years ago. Incidently, when you can do type I and type II trunking, it is called type IIi trunking. Anyway, when a portable requests a repeater, it sends an Inbound Signalling Word (ISW) to the the CSC who then decodes it. If it is a valid number, it will be processed just fine. If it is not a valid number for your CSC, it will be rejected and and the Unknown ISW diagnostic is generated.

We get them occasionally, maybe once a week. The city of Virginia Beach, about 20 miles away, gets them more than they want to. Here is what is happening and how they found out what was causing them. Your system is sitting there listening for inbound signalling words. It also hears signalling words from any other system that may be on the same frequency. Example. When Va. Beach and some place up in Baltimore are using the same freq for a control channel, then when the connect tone is open, mobiles trying to hit the Baltimore system are also hitting the Va. Beach system. And of course the CSC will not decode the Baltimore ISW. Plain and simple interference. They can change the control channel and the Unknow ISW's will go away.

If your customers are not getting any "Out of Range" then the problem is probably not your system.

To Check for this interference, put a spectrum analyzer on you control channel talk in frequency using a port off the recieve multicoupler and see if you can hear any other system on your talk in freq. Also, if you catch it doing it, change control channels and see if it goes away.

If you determine it is not interrference then there may be a problem with your fleet mapping and and announcement groups. Are you using a privacy plus system? Does this problem come and go? Did it start when you went to type IIi?



I hope this may give you a starting point. Any other questions, feel free to emails me at
rotzj@portsmouthva.gov

Regards. Joe

[KS4VT]

It could be someone who has a bootleg radio and it is trying to affiliate.