| 摘要 |
<p>1,212,907. Testing pulse repeater stations. SIEMENS A.G. 20 Sept., 1968 [21 Sept., 1967], No. 44753/68. Addition to 1,212,908. Heading H4L. The system disclosed in Specification 1,212,908 for testing intermediate stations in a P.C.M. system, wherein at a terminal exchange the normal P.C.M. signals are modulated by a low frequency wave for testing and at each intermediate station a pulse regenerator for the P.C.M. signals is followed by a bandpass filter responsive to the low frequency allotted to that station to operate a switch to feed back the test signal via a further pulse regenerator to the originating exchange or to feed it on to a further terminal exchange, is modified in that the filter operates in conjunction with a signal attenuator to reduce the signal fed to the further pulse regenerator to the level expected of a normal received signal.</p> |
