simplified ccis data transfer circuitry is shown for transmitting data between a ccis central processing unit of a central switching office and a number of terminal equipment controllers , each having a local cpu . the terminal equipment controller operates such equipment as modems of various speed , digital trunks or t1 spans . this design minimizes the amount of circuitry required to transmit ccis data between central processing units , thereby permitting a more reliable design . this circuit provides a minimal amount of logic required for interprocessor communication . in addition , this circuit minimizes the amount of real time required by each cpu to perform the ccis data transfer .