PURPOSE: To prevent leakage of talking contents to other party and intermission of talking due to intervention of other terminal equipment by releasing a means for turning off a switch between this set and each indoor terminal equipment with a handset hook-off signal from other terminal equipment based on an indoor terminal call signal from the other terminal equipment.

CONSTITUTION: When a handset 4 is hooked off and a handset 4 of other indoor terminal equipment 2 is hooked off already, the own terminal equipment 1 is not operated by the operation of an off-set means based on a handset hook-off signal from the other terminal equipment 2. When the handset 4 of the other indoor terminal equipment 2 is not hooked off yet, a talking switch 11 of the own terminal equipment 1 is closed by the operation of a set means 12a based on a gandset hook-off signal and an outdoor changeover switch 8 is also closed. On the other hand, an off setting release means 12c is actuated based on an indoor terminal call signal in the called indoor terminal equipment 2 and the talking switch 11 is closed when the handset 4 is hooked off.