An ISDN alarm notification (fault locating) system in subscriber
transmission equipment is connected to switching equipment conforming to
TR-303 standard, in particular. The system includes a controller for
setting switch options in subscriber transmission equipment externally,
in addition to a digital switch and subscriber transmission equipment.
The subscriber transmission equipment is provided with a switching
equipment interface unit, a control path unit, and an ISDN subscriber
interface unit. The controller sets the switch options provided in the
switching equipment interface unit, the control path unit, and the ISDN
subscriber interface unit. Thereby each switch option performs identical
function, corresponding to each digital switch connected to the
subscriber transmission equipment. Thus an ISDN alarm can be notified
accurately to any TR-303 digital switch even network terminals NT1 of
different types are connected to ISDN subscribers, and the compatibility
with conventional services (TR-008 POTS/ISDN, TR-303 POTS/ISD N) is
maintained.