Telephone exchange system to indicate cost of calls - redirects requests for call-cost from unused sub-exchange to sub-exchange in operation

摘要

The call-cost indicating system allows the stored cost of calls relating to a subscriber to be called up quickly on request by an exchange operator. The exchange comprises several sub-exchanges (e.g. night exchange). A request for call costs made to a sub-exchange not in use is redirected to another sub-exchange. When a second request is received by a sub-exchange already busy with a first request, the second request is held until this sub-exchange is free. If a third request to the same sub-exchange then occurs then it is redirected to the next free sub-exchange. All requests are held in a central memory if no sub-exchange is free. The requests thus stored are worked through in the order in which they were stored when sub-exchanges become free.