Abstract: A device is disclosed for use on a telephone line where there is two or more telephones or other instruments connected in parallel to the same telephone line whereby when one of the instruments goes off-hook (in a telephone, raises the receiver) the telephone line exclusion device automatically locks out all other instruments connected in parallel with the instrument that went off-hook. Such a result is achieved by a pair of interconnected two-coil polarized normally closed reed relays which interface the incoming telephone line and the two instruments. The two lines which normally connect to each instrument on the telephone line utilizes the normally closed contacts of one relay to energize the coils of the other relay and thereby inhibit the other instrument on the telephone line by opening the normally closed contact of the second relay which is in line with the other instrument.