Autopatch
Much in the same way your telephone does, substituting
RF for wires, your radio DTMF is the encoding device and the
receiver on the repeater is the decoding device and the tones you
send are simply transferred to the telephone switching devices
at the telco, a preset tone from your HT/radio will activate the
tone signalling device, once you hear dialtone in your radio, it works
just like using your telephone / cellphone, at the completion of your
call, a preset tone from you brings the patch down.....
Hope this helped some.
Most clubs with autopatches on their repeaters, charge for
memberships to pay the expenses, once you pay your dues the
signalling tones are give to you to use.