Call collision 40830 191945850 2008-02-16T23:01:03Z Jim.henderson 2255048 Subcat ->teletraffic In [[telecommunication]]s, a '''call collision''' (commonly known as '''glare''') is one of two things: #The [[contention]] that occurs when a [[terminal (telecommunication)|terminal]] and [[data]] [[Telecommunication circuit|circuit]]-terminating equipment ([[DCE]]) specify the same [[channel (communications)|channel]] at the same [[time]] to [[transfer]] a [[call]] request and handle an incoming call. When call [[collision]] occurs, the DCE proceeds with the call request and cancels the incoming call. #The condition that occurs when a [[trunk]] or channel is seized at both ends simultaneously. If you have ever tried to make a call out on a PBX, and been accidentally connected to an incoming call, you have experienced glare. This can sometimes happen at home too, if you pick up your phone to make a call out at the exact second that a call is about to start ringing in. [[Multi-line hunting]] generally avoids glare by picking trunks in opposite preference order so the highest numbered line, which is last choice for incoming calls, is first choice for outgoing calls, like so: <pre>incoming-->1 2 3 4 5 6 7 8<-- outgoing</pre> For PBX trunks, glare can further be reduced by using [[ground start]] trunking. IE: Nortel BSP discourages using [[loop start]] trunks for this and other reasons. Long Distance exchanges in the 1950s and 60s incorporated Glare Detectors to alleviate the problem. {{FS1037C MS188}} {{telecom-stub}} [[Category:teletraffic]]