I installed the M&S intercoms in my home. Main unit, 11 room units, 1 patio unit and the front doorbell unit. The sound has been good. I have had problems with the AM tuner playing a local station on a overtop of the correct station. Poor AM tuners can have this problem - I read up about it at the time - but can't remember the explanation now.
I also have the ELK M1 Gold and been happy with it.
The downside of using the auxillary audio connection to connect the voice output of the ELK M1 to the intercoms is that you must set the power on and input set to aux. One night someone had turned the music off by changing the M&S source to AUX where nothing was connected. I heard a humming all night that was low but annoying. In the morning I realized that the hum was from the intercom and the power was on. So this is the downside of leaving it on AUX. I had the same problem in my previous home with the Nutone intercom.
I experimented with the push button for the push to talk and found that by shorting a couple of the poles on I could activate the talk feature on an intercom room unit. I have purchased an ELK relay and was going to try to have the M1 or my computer activate this spare unit on command that I would locate near a computer or M1 speaker so that the intercom could carry the voice output when needed. Haven't done it yet.
If successful, that would mean that it would transmit voice output over the intercoms even when I'm playing music over the intercom. It would also mean the unit's power doesn't have to be on all the time.
One other thing I've experimented with was trying to connected the front doorbell to an input on the M1 so my security system/homeseer would know when someone pressed the bell. I was unsuccessful finding a way to do this. As I recall the doorbell is lighted and the wires carry a voltage (24v??) that was higher than the M1 was rated for. I asked ELK if they had any suggestions and they didn't at that time.
