摘要：The central system was instrumental in the formation of communication linksbetween the users of telecommunication services. Central phone that uses digitaltechnology has more advantages, some of them faster and more efficiently in theevent of a process of grafting. One type of digital telephone exchange used is theEWSD (Electronic Digital Switching Wahler), produced in Germany. EWSDtelephone exchange is divided into several functional units which is aninterconnected unity. Signalling system (signaling system) is an important partof telecommunications links. Signaling system is a set of signals that arerequired on the device EWSD, where its main function is to send an address,and control in connecting a phone call. In this signaling system has manyadvantages yaiu more efficient to use the canal.
