The URI requires a signal that pulls to ground in either active hi or low modes. Its not enough to see a voltage go hi or low. The signal from the radio MUST pull to ground or the URI will not see a change. If the COS/COR from your radio only sources voltage but doesn't pull to ground, then you need to use that line to drive an NPN transistor. (2N 3904 or 2N2222 will work).
You can put a 4.7 K resistor on the base and connect your radio's COS to that. Then connect the Emitter pin to ground and the Collector pin can be connected to your cor line on the URI. Then all you have to do is set the "Carrierfrom" to either USB or USBinvert in the USB radio config. This way the cor line from the transistor collector will pull to ground when the squelch opens in your radio.

Also note that using the transistor will invert your COS/COR signal. So if you have a voltage that goes high when the squelch opens then the O/P of your transistor will go low. Then set Carrierfrom to USBINVERT. (Active low).

Also to test this make sure you have your Ctcssfrom from set  to no. Once you have this working then you can add ctcss gating the same way. The CTCSS input on the URI also looks for a signal that pulls to ground. It doesnt care about applying a voltage to the pin.

Both the COR and CTCSS input lines on the URI have internal diodes to block incoming voltage. Again it only cares if the signal goes to ground or not.

Hope this helps.

Jon VA3RQ

On 3/7/2015 11:11 AM, Skyler F wrote:

How can I trigger the Allstar receiver when it gets a voltage from COS or switch 3 on the fob?

 Does it automatically trigger when a voltage is there? 

I added 5v to the COR URIx and did not get any trigger and I also tried closing SW3 on the home brew fob. Am I doing something wrong?

I will be getting a COS out on my radio and want to use The CTCSS on the radio instead of in AllStar.

Thanks 

Skyler