I incorporated 2 different solutions. Either one can be enabled or disabled by remote. In one case I made an oscillator in the audio frequency range at 1 Khz. This tone then injected into the phone line through the phone line coupler built for the DTMF encoder. Only 1 bit required to turn on and off the tone.
Software can issue a momentary burst of the tone or a sequence of bursts.
One bit is allocated to connect and disconnect the Audio card 'analog feed' to the Phone line Coupler. Now that gives remote control and Acknoledgment features to my system. First control assignment was X10. My requirements was it needed to be binary addressable and try and limit it to 8 bits. So I built an x10 encoder capable of all 256 channels.