Transmission and multiplexing - generic requirements of transport functionality of equipment - part 4 - 1 : synchronous digital hierarchy path layer functions endorsement of the english version en 300417 - 4 - 1 v 1 . 1 . 3 1999 - 05 as german stand 本标准规定对共电自动电话机技术条件gb 1493 - 79和磁石电话机技术条件gb 1494 - 79进行试验所应遵循的试验方法。