You can attached two standard telephones to this controller and it
will initiate a call when either phone goes
off-hook. The telephone that goes off hook first
will receive 2 seconds of dial tone. The other telephone will then begin
ringing until answered (factory default programming). The BUSY LED
will light on the controller when either telephone is off-hook and will
turn off during the duration of a timer and/or when both device ports
are on-hook. Note: Dial tone and/or ringing can be disabled. The
controller can be set for 4 different ring cadences (tones).
The distance between phones can be up to 2.6 miles total.