A Network Timing Concept for Switzerland

Abstract : Studies on network timing started in Switzerland in 1974, pre paring the future conversion to digital transmission and switching, stimulated by the development of integrated electronics. First generation equipment was specified and developed in 1975/76, when early international standards recommending 10-11 long term stability were drafted. Further work led to the present network timing concept in which the network is divided into 3 regions, each cesium-controlled in a preselected master-slave mode with 4 levels of hierarchy. All major (2nd order) nodes are served by triple-redundant, microprocessor-controlled precision crystal oscillators. The third order level is constituted by the digital switching centers.