Call forwarding, or call diversion, is a telephony feature of some telephone switching systems which redirects a telephone call to another destination, which may be, for example, a mobile telephone, voicemail box or another telephone number where the desired called party is available. Call forwarding was invented by Ernest J. Bonanno. In North America, the forwarded line usually rings once to remind the customer using call forwarding that the call is being redirected. More consistently, the forwarded line indicates its condition by stutter dial tone. 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. Call forwarding is often enabled by dialing *72 followed by the telephone number to which calls should be forwarded. Once someone answers, call forwarding is in effect. If no one answers or the line is busy, the dialing sequence must be repeated to effect call forwarding. Call forwarding is disabled by dialing *73. This feature requires a subscription from the telephone company. 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.
In Europe, most networks indicate that unconditional call forwarding is active with a special dial tone. When the phone is picked up it is immediately apparent that calls are being forwarded.
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".
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.
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. In North America, the NANP generally uses the following vertical service codes to control call forwarding:
|Forward service||Activation||Deactivation||Number change|
|All calls||*72 and 10 digits local phone number (some larger cities require *72 and 1 and 10 digits)||*73|
|On busy or no answer||*68||*81|
|From select callers||*63||*81|
|Customer-programmable features (where available):|
|On busy or no answer||*28[phone number]||*38|
|On busy||*74[phone number]||*740|
|On no answer||*73[phone number]||*730|
- As of Jan 2012, Sprint charges 20 cents per minute for unconditional call forwarding, conditional call forwarding is included however.
- Some carriers (including Verizon Wireless) use *71 for conditional forwarding although this is not standard.
- Sometimes, to deactivate a call forwarding, *720 will work on cellphones.
Most EU fixed-line carriers use the following codes based on CEPT and ETSI standards developed in the 1970s on both POTS and ISDN lines: (There may be some variation to these, but the unconditional code *21*, is very much universally standard on EU telephone lines.) The general syntax for all European service codes always follows the pattern below:
|Forward service||Activate||Cancel & Deregister||Cancel & Retain||Status||Reestablish|
|all calls (unconditionally)||*21*[phone number]#||#21#||#21#||*#21#||*21#|
|if busy||*69*[phone number]# or *67*[phone number]#||#69# or #67#||#69# or #67#||*#69# or *#67#||*69# or *67#|
|if not answered||*61*[phone number]#||#61#||#61#||*#61#||*61#|
For GSM/3GSM (UMTS) phones, the GSM standard defines the following forwarding codes. These were developed by ETSI and are based on standard European diversion codes and are similar to those used on most landlines in the EU:
|Forward service||Activate||Cancel & Deregister||Cancel & Retain||Status||Reestablish|
|all calls||*21*[phone number]#||##21#||#21#||*#21#||*21#|
|if busy||*67*[phone number]#||##67#||#67#||*#67#||*67#|
|if not answered||*61*[phone number]#||##61#||#61#||*#61#||*61#|
|if out of reach||*62*[phone number]#||##62#||#62#||*#62#||*62#|
|all forwards||*002*[phone number]#||##002#||#002#||*#002#||*002#|
|all conditional forwards||*004*[phone number]#||##004#||#004#||*#004#||*004#|
If the prefix to the forwarding command is "**" (instead of the usual "*"), then the phone number in that command is registered in the network. If after that the forwarding is deactivated using a command with a single "#", then later it will be possible to re-activate this forwarding again with a simple "*" command without a phone number in it. The forwarding will be re-activated to the number registered in the network. For example, if one uses the out-of-reach code in a forwarding command:
and after that one deactivates the forwarding:
then later it will be possible to re-activate the out-of-reach forwarding without specifying a number:
After the above command, all calls made to the phone, while it is out of reach, will be forwarded to 7035551212. It is possible to activate the feature to a number other than the registered number, whilst still retaining the registered number for later use. For example, issuing the command:
will result in calls being forwarded to 7185551212 (and not to the registered number 7035551212). However, if later a command is issued:
then the calls will again be forwarded to the registered number 7035551212 (and not to the number from the previous forwarding command 7185551212).
Additionally, in GSM networks, such as T-Mobile and AT&T Mobility in USA, and all mobile networks in EU, it is possible to set the number of seconds the phone will ring before forwarding. This is specified by inserting "*SC*XX" prior to the final "#" of the forwarding command, where "SC" is a service type code (11 for voice, 25 for data, 13 for fax), and "XX" is the number of seconds in increments of 5 seconds. If "SC" is omitted (just "**XX") then by default all service types will be forwarded. For example, forwarding on no-answer can be set with:
In some networks there may be a limit of not more than 30 seconds before forwarding (i.e. "XX" can only be 5, 10, 15, 20, 25 or 30; all greater values, like 45 and 60, will result in the forwarding command being rejected and an error message returned).
Diverting calls can increase one's availability to a caller. The main alternative is an answering machine or voicemail, but some callers do not wish to leave a recorded message, suspecting that the party will delay returning their messages. A caller at a telephone booth may be unable to receive the call if a recorded message is returned.
Some businesses find that the human touch can improve contact, thus sales, but traditional wired answering services are expensive, so they have their calls forwarded to a call center, so the client can reach an operator instead of an answering machine or voice mail.
Often, a suburb of a large city is a toll call from many suburban exchanges on the opposite side of the same city, even though all of these suburbs are a local call to the city centre. A business located in such a suburb may therefore benefit from obtaining a downtown number as an "extender", to be permanently forwarded to their geographic suburban number.
Where unlimited local calls are flat-rated and long-distance incurs high per-minute charges, the downtown number's wider local calling area represents a commercial advantage. Markham (directly north of Toronto) is long-distance to Mississauga (directly west of Toronto) . A Markham business with a forwarded area code 416 Toronto number could receive calls from Malton airport in Mississauga without incurring long-distance charges (as Malton → Toronto and Toronto → Markham are each a local call).
Some services offer international call forwarding by allocating for the customer a local virtual phone number which is forwarded to any other international destination. As a means to obtain an inbound number from another town or region for business use, call forwarding schemes tend to be far less expensive than foreign exchange lines but more costly than using voice over IP to obtain a local number in the chosen city.
- Bonanno, Ernest J. (1963-09-24). "CA 671260 - Call Forwarding Arrangement". Canadian Patents Database. Canadian Intellectual Property Office. Retrieved 2010-08-11.
- ETSI (1995-01-04). "ISDN Diversion supplementary services ETS 300 207". ISDN Specification. European Telecommunications Standards Institute. Retrieved 2011-10-26.
- "Find out more about call forwarding". Support and Services. Sprint.com. Retrieved 2010-05-22.[dead link]
- "iPhone 4S/Call Forwarding". Support and Services. Sprint.com. 2012-01-17. Retrieved 2012-06-24.
- "Calling features: No Answer/Busy Transfer". Support. Verizon Wireless. Retrieved 2012-06-24.
- "GSM feature codes". Tips and Secrets. Gecko Beach. Retrieved 2010-07-26.
- Call Forwarding User manual, Bell Canada