Comments on the Components Used in Modules of S.C.U.

There is a serious competition for the coding filtering module and the proposed solutions are satisfactory from the point of view of performance, price, consumption and volume. No agreements concerning neither exact functions nor the realization of S.S.M. (Subscriber Signalisation Module) have been arrived at. There are enormous possibilities of evolution in this field which is heading towards a standardization. The three difficult points are: 1) the increase in voltage capabilities of the semiconductors can simplify the protection module; 2) systematic use of low-loss power supplies in the exchange (microphone current obtained by using the high efficiency power supplies, for example switched power supplies); 3) use of hybrid circuits for the 2/4 wire transformers with the subscriber line impedance matching.