Taking the TX inhibit pin on the ACC connector high inhibits transmission (although the radio still switches to transmit mode). ?I've read some posts in various places which talk about the 817 sensing when a plug is inserted into the ACC socket and causing the line to be pulled high so that you have to actively pull it low in order to be able to transmit. ?I haven't actually verified this (it's certainly not the case on digital modes in my experience) but at least one discussion (on the AMSAT site I think) claims to have verified this by experiment. ?However, I've looked at the schematic and can't see any obvious evidence of this. ?But whether there's a sensor or not, pulling the line high (greater than 5 volts) will inhibit transmission and pulling it low will enable it. ?Hope that helps.
73. De John M0ACN
