PACKET AND CIRCUIT SWITCHED COMMUNICATIONS NETWORK

一分组交换和电路变换的通信网由包括呼叫控制单元在内的多个单元组成。每个单元都与数据线、地址线和控制线相连，数据线用来传输呼叫控制单元和其它单元间呼叫控制信号以及呼叫和被呼叫单元间的通信信号。为了决定这些单元到数据线的进出通道，总线控制器通过地址和控制线与其单元相连，故仅有一个单元可以在任何时刻进行传输。总线控制器包含有：查询电路；对请求作出响应的许可电路，以及同步周期电路。 A telecommunications network (Fig. 1) being operable as a packet switch and as a circuit switch is comprised of a plurality of units including a call controller unit. Each of the units is connected in common to data (607), address (610), and control leads (221, 224, 225, 613-618) of a bus, the data leads being commonly available for signal transmissions of both call control signals between the call controller unit and the other units and communications signals between calling and called ones of the other units. A bus controller (Fig. 2) is connected to the units by way of the address and control leads for arbitrating access to the data leads by the units, so that only one unit may transmit at any one time. The bus controller includes, a poll circuit (300) for polling the units for asynchronous transmission requests, a grant