[TELECOM Digest Editor's Note: Thanks for that good explanation.
> it was interesting that he was able to 'communicate by voice' over
> those wires which served as our burglar alarm system; he said it was
I knew some guys in the Chicago suburbs circa 1965 who had their own private telephone system among them. They had learned it was possible to lease burglar alarm lines very cheaply from the telephone company; and in fact when you leased one you got an ordinary wire pair that worked just fine at voice frequencies. So that was what they used for their distribution. Eventually the phone company got onto what they were doing and connected large capacitors across the pairs, which put an end to their scheme.
jhhaynes at earthlink dot net