Electronic switching system having call-forwarding function

Claim 2

An electronic switching system having a call-forwarding function for effecting a call forward between subscribers, comprising: a plurality of subscriber terminals; a switching network accommodating said subscriber terminals; a storage unit, connected to said switching network, for storing data used to forward calls for said subscriber terminals; a discrimination information adding means, connected to said storage, for adding discrimination information to said data for respective subscriber terminals, said discrimination information indicating whether or not each of said subscriber terminals is already registered as an alternative destination from another subscriber terminal accommodated by said switching network; a discrimination information reading means, connected to said discrimination information adding means, for reading, when a call forward from one of said subscriber terminals to another of said subscriber terminals is to be registered into said storage, said discrimination information of said another of said subscriber terminals; whereby, when the read discrimination information indicates that said another of said subscriber terminals is not registered as an alternative destination, said another of said subscriber terminals is allowed to be registered as an alternative destination, and when the read discrimination information indicates that said another of said subscriber terminals is already registered as an alternative destination, said another of said subscriber terminals is inhibited from being registered as an alternative destination.

Claim 3

An electronic switching system as claimed in claim 1, wherein said call forwarding is executed for an absent transfer state.

Claim 4

An electronic switching system as claimed in claim 1, wherein said call forwarding is executed for a call forwarding busy line state.

Claim 5

An electronic switching system as claimed in claim 1, wherein said call forwarding is executed for a call forwarding don't (no) answer state.

Claim 6

An electronic switching system as claimed in claim 1, further comprising: a storage area for storing, during an execution of a call forward, first subscriber information of the first subscriber terminal (A) which is the first incoming terminal and which is registered as a terminal for forwarding the incoming call to another subscriber terminal (B); a comparing means, connected to said storage area, for comparing, when said another subscriber terminal (B) is registered as a terminal for forwarding the incoming call to still another subscriber terminal (C), said first subscriber information of said first subscriber terminal (A) with another subscriber information of said still another subscriber terminal (C); whereby, as a result of the comparison, when said first subscriber information coincides with said other subscriber information, the forwarding to said still another subscriber terminal (C) is inhibited; and when said first subscriber information does not coincide with said other subscriber information, the forwarding to said still another subscriber terminal (C) is allowed.

Claim 7

An electronic switching system as claimed in claim 1, further comprising: call forwarding means for forwarding a call from said electronic switching system to another electronic switching system; said another electronic switching system comprising: a plurality of subscriber terminals; a switching network accommodating said subscriber terminals; a storage means, connected to said switching network, for storing data used to call forward for said subscriber terminals; a discrimination information adding means, connected to said storage, for adding discrimination information to said data for respective subscriber terminals, said discrim­ination information indicating whether or not each of said subscriber terminals is already registered as an alternative destination from another subscriber terminal; a discrimination information reading means, connected to said discrimination information adding means, for reading, when a call forward from one of said subscriber terminals to another of said subscriber terminals is to be registered into said storage, said discriminating information of said another of said subscriber terminals; whereby, when a call transfer between said switching system is to be registered, and when the read discrimination information indicates that said another of said subscriber terminals is not registered as an alternative destination, said another of said subscriber terminals is allowed to be registered as an alternative destination, and when the read discriminating information indicates that said another of said subscriber terminals is already registered as an alterna­tive destination, said another of said subscriber terminals is inhibited from being registered as an alternative destination.

Claim 8

An electronic switching system as claimed in claim 6, wherein control signals between said electronic switching systems are transmitted and received through a common signaling link.

Claim 9

An electronic switching system having a call-forwarding function for effecting a call forward between subscribers, comprising: a plurality of subscriber terminals; a switching network accommodating said subscriber terminals; a storage means, connected to said switching network, for storing data used to call forward for said subscriber terminals; a discrimination information adding means, connected to said storage means, for adding discrimination information to said data for respective subscriber terminals, said discrimination information indicating whether or not each of said subscriber terminals is already registered as an alternative destination from other subscriber terminals accommodated by said switching network; a discrimination information reading means, connected to said discrimination information adding means, for reading, when a call forward from one of said subscriber terminals to another of said subscriber terminals is to be registered into said storage means, said discrimination information of said one of said subscriber terminals; whereby, when the read discrimination information indicates that said one of said subscriber terminals is not registered by another subscriber terminal as an alternative destination, said another subscriber terminal is allowed to be registered as an alternative destination, and when the read discrim­inating information indicates that said one of said subscriber terminals is already registered by another subscriber terminal as an alternative destination, said another subscriber terminal is inhibited from being registered as an alternative destination.

Claim 10

An electronic switching system having a call-forwarding function for effecting a call forward between subscribers, comprising: a plurality of subscriber terminals; a switching network accommodating said subscriber terminals; a storage means, connected to said switching network, for storing data used to call forward for said subscriber terminals; a discrimination information adding means, connected to said storage means, for adding discrimination information to said data for respective subscriber terminals, said discrimination information indicating whether or not each of said subscriber terminals is already registered as an alternative destination from other subscriber terminals accommodated by said switching network; a discrimination information reading means, connected to said discrimination information adding means, for reading, when a call forward from one of said subscriber terminals to another of said subscriber terminals is to be registered into said storage means, said discrimination information of said one of said subscriber terminals; whereby, when the read discrimination information indicates that said one of said subscriber terminals is not registered by another subscriber terminal as an alternative destination, said another subscriber terminal is allowed to be registered as an alternative destination, and when the read discrim­inating information indicates that said one of said subscriber terminals is already registered by another subscriber terminal as an alternative destination, said another subscriber terminal is inhibited from being registered as an alternative destination.

Claim 11

An electronic switching system as claimed in claim 8, wherein said call forwarding is executed for an absent transfer state.

Claim 12

An electronic switching system as claimed in claim 8, wherein said call forwarding is executed for a call forwarding busy line state.

Claim 13

An electronic switching system as claimed in claim 8, wherein said call forwarding is executed for a call forwarding don't answer state.

Claim 14

An electronic switching system as claimed in claim 8, further comprising: call forwarding means for forwarding a call from said electronic switching system to another electronic switching system; said another electronic switching system comprising: a plurality of subscriber terminals; a switching network accommodating said subscriber terminals; a storage means, connected to said switching network, for storing data used to call forward for said subscriber terminals; a discrimination information adding means, connected to said storage means, for adding discrimination information to said data for respective subscriber terminals, said discrimination information indicating whether or not each of said subscriber terminals is already specified as an alternative destina­tion from other subscriber terminals; a discrimination information reading means, connected to said discrimination information adding means, for reading, when a call forward from one of said subscriber terminals to another of said subscriber terminals is to be registered into said storage means, said discrimination information of said one of said subscriber terminals; whereby, when the read discrimination information indicates that said one of said subscriber terminals is not registered by another subscriber terminal as an alternative destination, said another subscriber terminal is allowed to be registered as an alternative destination, and when the read discriminating information indicates that said one of said subscriber terminals is already registered by another subscriber terminal as an alternative destination, said another subscriber terminal is inhibited from being registered as an alternative destination.

Claim 15

An electronic switching system as claimed in claim 7, wherein control signals between said electronic switching systems are transmitted and received through a common signaling link.