of receiving the maximum total used in the national system. With nonuniform numbering, an incompletely dialed call can cause a useless call setup across a network up to the terminating exchange, and the call setup is released only after time out has run its course. It is evident that with nonuniform numbering systems, national (and international) networks are better suited to signaling systems operating end to end with good features of backward information, such as the R-2 system (Ref. : 5). 7.7 ASSOCIATED AND DISASSOCIATED CHANNEL SIGNALING Here we introduce a new concept: disassociated channel signaling. Up to now we have only considered associated channel signaling. In other words, the signaling is carried right Exchange A Trunks Exchange B Signal Signal Switch Switch network network sender receiver Processor Processor Associated Channel Signaling (Conventional SF-MF) Exchange A Trunks Exchange B Switch Switch network network Processor Signaling terminal Processor terminal Separate Channel Signaling Figure 7.5 Conventional analog associated channel signaling (upper) versus separate channel signaling (which we call quasi-associated channel signaling) (lower). Note: Signaling on upper drawing accompanies voice paths; signaling on the lower drawing is conveyed on a separate circuit (or time slot). CCS stands for common channel signaling such as CCITT Signaling System No. 7. 4"Timeout" is the resetting of call-setup equipment and return of dial tone to subscriber as a result of incomplete signaling procedure, subset left off hook, and so forth. 7.7 ASSOCIATED AND DISASSOCIATED CHANNEL SIGNALING Speech Signaling links Switching points Figure 7.6 Quasi-associated channel signaling, typical of E-1 channel 16. As shown, the signaling travels on a separate channel but associated with its group of traffic channels for which it serves. If it were conventional analog signaling, it would be just one solid line, where the signaling is embedded with its associated traffic. Speech network Signaling network Switching points (s