US 5099511

Patent Overview — US5099511A

Title: Exchange system for incoming calls from direct-in lines

Patent number: US5099511A (application US07/448,840)

Assignee: Fujitsu Ltd (original assignee; assignment recorded 1989-12-12, assignor Masaharu Matsumoto)

Inventor: Masaharu Matsumoto

Priority date: 1988-12-12 · Filing date: 1989-12-12 · Publication/grant date: 1992-03-24

Legal status (as listed): Expired – Lifetime; anticipated expiration 2009-12-12.

Classifications: H04M3/38 (graded-service arrangements); H04Q3/625 (PBX arrangements); H04M3/533 (voice mail systems).

Purpose. The patent addresses a problem in private branch exchange (PBX) systems serving direct-in lines (DID/DISA, including ISDN). In the prior art, class-of-service was assigned to the incoming trunk itself, so "the number of trunks which can offer a particular service such as origination of call to the office line may be restricted," making "the application efficiency of incoming trunks … low."

Plain-language scope. The system's control unit converts additional information arriving from the direct-in line—either second dial information or information in a call set-up message, such as the termination subaddress—into class-of-service information. A restriction table maps that class-of-service information to allowable services; the table is indexed by the class-of-service information to retrieve which services are permitted. The class-of-service information distinguishes restriction of outgoing connection service (repeating connection) from restriction of station service. A security code, formed from a determined number of digits at the leading or ending part of the additional information, is used and converted to the restriction class. This lets the service class be set "for each originating subscriber of external ISDN terminal units having the dial-in function," rather than per trunk. The described PBX network includes a message analyzing part, a dial digit deciding part, and a call controller.

Source: https://patents.google.com/patent/[US5099511](/patent/US5099511)/en

What the excerpt does not establish. The supplied text is explicitly an excerpt with omitted portions; it does not include the full claims, the complete detailed description, or the drawing contents (FIGS. 1–4 are referenced but not reproduced). It also does not establish prosecution history, the scope of any specific claim, or the accuracy of the listed legal status. No litigation, ownership-transfer, validity, or prior-art analysis was performed.