[aprssig] What is "TNC Channel Switching"?

[Stephen H. Smith]

On 4/11/2014 9:47 AM, Andrew Pavlin wrote:
> The KAM Plus was a dual band TNC, so one serial port could give you access to two radios at the same time, generally HF and VHF. It also could automatically gate between the two. I think the same scheme was used on the 9612 which was 1200 and 9600 baud simultaneous. The stream switch would tell the TNC which band to send a packet. I don't recall if they listened for stream switches from the RF side. You definitely should not send them on a serial port unless you have a way to disable it or unless you state your code is incompatible with the KAM and KPC 9612. There still are some floating around. Generally, best to follow the spec on things like this.

They didn't "listen" for the steam switch.   When "normal" packets from either 
radio were received, they were prefixed with the appropriate switch character 
before being sent out the serial port to the attached terminal.

If the attached "terminal" was a dual-port-aware program running on a computer, 
it could automatically direct the incoming packet to the correct half of a 
split-screen display.