The provision of a Carrier operated squelch or COS can be useful if one is attempting to use a transceiver as a node radio in the service of Echolink, IRLP, Allstar or Wires-X analog system. COS is used to detect an FM carrier on the radio receive side of the node and lets the computer know that a RF signal has been detected so that the received signal can be routed to the system server or local controller in the case of Wires-X.
Using the Baofeng BF888, which is a very inexpensive radio ( less than $20 ) is great value anyway but when used as a node radio it's even better.This simple modification does not require any major alteration to the radio.
The process of implementing this feature is explained with the help of the following picture, its shows how to connect a wire to pin 1 of audio IC type BL6281 at top left hand side which is routed to a 0.1 mm single female crimp connector housing glued in between mic and speaker jack on the side of the radio.
A single solid wire maybe be feed through the rubber grommet around the mic/speaker jack and wire to the node controller interface or Wires-X HRI200 box.
When the radios squelch is activated by a received FM signal, the voltage on pin 1 of IC goes from 0 to 2.8v, this can be configured as a carrier detect in the settings of the interface unit.
