In North America, the North American Numbering Plan (NANP) generally uses the following vertical service codes to control call forwarding:Ĭustomer-programmable features (where available): Special types of call forwarding can be activated only if the line is busy, or if there is no answer, or even only for calls from selected numbers. The terms call forwarding and call diversion are both used to refer to any feature that allows a call to be routed to a third party, and the terms are generally interchangeable. The ISDN Diversion supplementary services standards document uses "diversion" as a general term to encompass specific features including "Call Forwarding Busy", "Call Forwarding No Reply" and "Call Deflection". When the phone is picked up it is immediately apparent that calls are being forwarded, while in other countries same system is being followed now. In Europe, most networks indicate that unconditional call forwarding is active with a special dial tone. VOIP and cable telephone systems also allow call forwarding to be set up and directed via their web portals. Also available in some areas is Remote Access to call forwarding, which permit the control over call forwarding from telephones other than the subscriber's telephone. This feature requires a subscription from the telephone company. Call forwarding is disabled by dialing *73. If no one answers or the line is busy, the dialing sequence must be repeated to effect call forwarding. Once someone answers, call forwarding is in effect. Call forwarding is often enabled by dialing *72 followed by the telephone number to which calls should be forwarded. Call forwarding typically can redirect incoming calls to any other domestic telephone number, but the owner of the forwarded line must pay any toll charges for forwarded calls. More consistently, the forwarded line indicates its condition by stutter dial tone. In North America, the forwarded line usually rings once to remind the customer using call forwarding that the call is being redirected. Call forwarding was invented by Ernest J. Call forwarding, or call diversion, is a telephony feature of all telephone switching systems which redirects a telephone call to another destination, which may be, for example, a mobile or another mobile or another telephone number where the desired called party is available.