Call forwarding
Call forwarding, orcall diversion, is a telephonyfeature 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 numberwhere the desired called
partyis 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.
Terminology
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 termscall forwardingandcall diversionare both used to refer to any
feature that allows a call to be routed to a third party, and the
terms are generally interchangeable. ↑Jump back a section
Keypad codes
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 NANPgenerally uses the following
vertical service codesto 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
On ISDN *56
Customer-programmable features (where available):
Busy line *90*91*41
No answer *92*93*41
The Sprint Nextelcellphone company uses these:
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
*.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 CEPTand
ETSIstandards developed in the 1970s on both POTSand ISDNlines: (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 GSMstandard 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
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* MOB # ##61# #61# *#61# *61#
if out of reach*62* MOB ###62# #62# *#62# *62#
all forwards *002* MOB # ##002# #002# *#002# *002#
all conditional forwards*004* MOB #
##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#
Deactivates :
To all status dial ##002# For gsm.
