pay phones are no different than any other phone. They DON'T have their own low voltage line. They get their voltage from the phone line just like all other phones. The difference with the older phones, are they had REAL RINGERS. Not the chirping pizo type ringers of today's phones. As such, they like old desk phones with real bells, draw a lot of current. So if you want to hook up an ATA to your jacks, you just need to make sure you don't have too many bells turned on. Or else it will ring-trip. Which means, it will do a half of a ring and basically lock up the call. I have 10 phones connected to my ATA through the house. I have the bells working on the 1910 Country Junction phone; one phone down stairs; and one in the bedroom. Between these three phones ringing, you can hear the phone ringing anywhere in the house. I simply turn the ringer off of the other phones.