How do XM Radio subscriptions work?

Question

Radios are one way, right? They recieve signals? So how does an XM satellite know to stop broadcasting the signal to a radio if the subscription hasn't been updated?

PS, the XM salesperson at my local mall didn't know.

And I *will* be awarding points for this.

Answer 1

Each device capable of satellite radio has an electronic serial number that is assigned to it. When you activate the device a signal is sent to the satellite telling it that this particular number now has access to a particular set of channels. If the service is terminated the satellite basically blocks all the channels. I can't say for certain, but I believe that there is a test channel that will work regardless of whether the service is active or not. I think it is a weather channel which doubles as a test channel to make sure the unit has reception.

Answer 2

bigdog820 is right. XM radio is just like satellite TV. When you subscribe, you give the company the receivers serial number. The company sends a signal out that tells that receiver to decode the satellite signal provide service. If you unsubscribe, the company sends a signal out the tells that receiver to disable the decode process and not provide service.