Call forwarding (or call diversion), in telephony, is a feature on some telephone networks allowing an incoming call to a called party to be redirected to a third party. For example, the third party may be a mobile telephone, voicemail box or other telephone number where the desired called party is situated. It was invented by Ernest J. Bonanno.[1] In North America, the forwarded line usually (though not always) 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.
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.
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The ISDN Diversion supplementary services[2] standards document uses "diversion" as a general term to encompass specific features including "Call Forwarding Busy", "Call Forwarding No Reply" and "Call Deflection".
In common language, 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 | *88 | |
| From select callers | *63 | *83 | |
| On ISDN | *56 | ||
| Customer-programmable features (where available): | |||
| Busy line | *90 | *91 | *40 |
| No answer | *92 | *93 | *42 |
The Sprint Nextel cellphone company uses these:[3]
| Forward service | Activation | Deactivation |
|---|---|---|
| On busy or no answer | *28[phone number] | *38 |
| On busy | *74[phone number] | *740 |
| On no answer | *73[phone number] | *730 |
| Immediately | *72[phone number] | *720 |
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 |
|---|---|---|---|---|---|
| Unconditional forwarding: | |||||
| all calls (unconditionally) | *21*[phone number]# | #21# | #21# | *#21# | *21# |
| Conditional forwarding: | |||||
| 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:[4]
| Forward service | Activate | Cancel & Deregister | Cancel & Retain | Status | Reestablish |
|---|---|---|---|---|---|
| Unconditional forwarding: | |||||
| all calls | *21*[phone number]# | ##21# | #21# | *#21# | *21# |
| Conditional forwarding: | |||||
| 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:
**62*7035551212#
and after that one deactivates the forwarding:
#62#
then later it will be possible to re-activate the out-of-reach forwarding without specifying a number:
*62#
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:
*62*7185551212#
will result in calls being forwarded to 7185551212 (and not to the registered number 7035551212). However, if later a command is issued:
*62#
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:
*61*[phone number]*[seconds]#
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.
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.
Some services offer international call forwarding by allocating for the customer a local virtual phone number which is forwarded to any other international destination.
How To Forward Your Calls on cell phone