Microprocessors in switching system control

Abstract Microelectronics is rapidly entering the field of communication switching in all areas of control: in the line and trunk units, in the actual switching network, and in the coordinating processors. Standard, i.e., “off the shelf” microprocessors and high-density memory chips are being deployed by most manufacturers. Relying upon EWSD - the digital public switching system from Siemens - as an example it will be demonstrated that such a second generation approach yields the expected results. Within EWSD all types of line or trunk terminating units operate under microprocessor control. The same holds for the switching network. And even the coordination processor for small-to-medium sized offices uses the same microprocessor setup. Switching system control embarks into the microelectronic age almost directly from its still prevailing electromechanical past. But there are merits in this late change. The three “C's”, i.e., components, computers, and communications have reached sufficient maturity for this transition.