procedures for redial in a centrally controlled fernsprechvermittlungssystem, particularly in a centrally controlled fernsprechnebenstellenanlage with a data memory

摘要

The telephone exchange has compartmentalized data storage facilities allotted to groups of subscribers for optional use additional to the usual command and address storage units and the speech channel couple field, and provides the possibility for a part of the subscriber stations-responsive to a first demand signal - to be allotted a digital storage facility for automatically re-dialling the number of a called party. If such a first demand signal is used, and if the called subscriber answers, there is no need for any re-dialling, yet the allotted storage space remains associated with the calling station. Therefore, all subsequent numbers called are also temporarily stored, replacing the earlier ones. If any called party is engaged the calling party, to obtain automatic re-dialling, enters a second demand signal. Any station holding a storage location without having had to use it may lose it when all the storage places are occupied and at least one further request for the re-dialling storage facility is being made by a member of the subscriber group concerned. In that case, the storage space of that subscriber who has held it longest is taken from him and transferred to the newly demanding station.