| 摘要 |
1283823 Automatic exchange systems SIEMENS AG 7 Aug 1970 [8 Aug 1969] 38158/70 Heading H4K In a centrally controlled cross-bar exchange load shedding occurs whenever the ratio of the number of control operations required in establishing or disconnecting paths through the switching network to the number of other control operations falls below a predetermined limit. " Other control operations " comprise operations performed in respect of certain special services, e.g. camp-on busy (door-knocking) and call relaying (call diversion put into effected by the special called subscriber having previously dialled a special command into the exchange) wherein network paths and control apparatus are tied up without participating in an active call and wherein additional facilities are requested by an existing call, and, additional features, e.g. alternative routing wherein an excessive number of network paths are occupied and/or an excessive number of data exchanges between a marker and a translator are necessary in respect of a same call or wherein complex checks are made that paths which should have been released have in fact been disconnected. The system markers in particular are monitored to assess the value of the ratio so that if this falls below the required value the " other operations " become curtailed preferably on an order of priority basis which is governed by the degree of undershoot of the limit. Restoration to normal takes place as the limit is exceeded. The system is distinguished from German Specification DAS 1,242,713 and PDS 919,241 in which, effectively, calls from low priority subscribers are barred during overload conditions. |
