机电交换机的发展,把基本部件分成两类:A)一类是建立呼叫和被呼叫用户间联结的部件——通话电路.B)一类是授与通话电路所必需的指令部件——控制电路.后者是一种简单的专用计算机,它包括存储器和逻辑电路,存储器包含描述系统状态的信息,而逻辑电路能够按照已寄存的或新的数字,把准备的信息传给通话电路.因此,近代交换机包括通话电路、逻辑电路和存储器. The development of electromechanical switches, the basic components into two categories: A) one is the establishment of the call and the called user link between the components - call circuit .B) is a class of instruction and call the necessary circuit instruction components - control circuit. The latter is a simple, dedicated computer that includes memory and logic that contains information that describes the state of the system, and logic that conveys the prepared information to the calling circuit in accordance with the registered or new digits. Thus, The switch includes the call circuit, logic circuit and memory.