Abstract: A telephone fault detection system particularly suitable for use with a home telephone system is provided. The system includes a switching circuit coupled to a telephone company trunk line and to telephone customer equipment. In particular, the telephone customer equipment includes at least a monitoring device, such as a telephone handset, and at least one further telephone handset. When the switching circuit is in a first normally operative mode, the monitoring device and the telephone handset are coupled to the trunk line so that the monitoring circuit can provide indication of a fault condition on either the telephone company trunk line side or the internal telephone system side of the switching circuit. When the switching circuit is disposed in a second test mode, the additional telephone handsets are decoupled from the telephone trunk line and the monitoring device detects the location of the fault condition in either the telephone trunk line or the internal telephone system.

Abstract: A telephone fault isolation device is installed between customer telephone equipment, such as a PBX or KSU, and telephone company trunk lines feeding into such equipment, and is used to determine whether possible trouble is in the telephone company trunk lines or in the customer equipment. The device includes a monitoring device, such as a telephone handset, and an array of switches each associated with a telephone trunk line. Each of the switches, in a normal condition, connects the trunk line to the equipment, and, in a test condition, connects the trunk line to the monitoring device. A telephone customer can switch over each of the switches in turn and determine whether he can obtain dial tone on that respective trunk line.