Here is another way I might do basically the same thing but instead using my Diodes on a separate PCB Board and the Relays mounted to another board. I have not yet decided yet. So far the only thing I am pretty set on is having one wire going to the Voice Box to request the DTMF tone. The single wire will connect a ground pulse to activate a single small relay mounted close to the Voice Box, the switch side of that Relay will make connection on the Voice Box by connecting the DTMF Tone Request to the Ground on the Voice Box. That way the wires requesting the actual tone will be kept to a minimum and be as short as possible to help prevent any signal interference which I understand can sometimes happen if the DTMF tone request wires are too long. This will also well isolate the DTMF tone request from the actual switches needing to request that tone.