If for connection to an Amateur Radio for legal use, there are sufficent designs in existance. If you're designing to cater to the rogue CB crowd, might I recommend designing in a device which results in immediate electrocution, as soon as the operator presses the microphone button, enough to complete a PTT connection. Or at least, impart the equivalent of a high-powered stungun, to the operators' cerebral cortex, or privates.