Right, I have broken out a COR line from my radio (+5v when a carrier is detected). What do I do with it now? I've tried going via a resistor and diode into the PP, pin 15 but the node is permanently locked into RX regardless of any connection. My usbradio.conf is pasted below: [usb29681] hdwtype=0 rxboost=1 txboost=1 rxctcssrelax=1 ;#txctcssdefault=100.0 ;#rxctcssfreqs=100.0 ;#txctcssfreqs=100.0 ;rxctcssoverride=0 carrierfrom=pp pp15=cor ctcssfrom=no rxdemod=speaker txprelim=no txlimonly=no txtoctype=notone txmixa=voice txmixb=no invertptt=0 duplex=0 rxondelay=0 rxnoisefiltype=0 eeprom=0 PP in BIOS is set to Bi Directional (assuming it makes a difference?). If I have to, I'll go on to pin 47 (I think) of the CM108 chip, but I'd rather try the PP method first! Cheers, J