Call forwarding
Call forwarding is a phone-network feature that sends calls placed to your number on to another number. Unconditional forwarding sends every call the moment it arrives, so your own phone never rings. Conditional forwarding sends a call only when you do not answer, the line is busy, or your phone is unreachable.
Key facts
- The 3GPP mobile standard defines four call-forwarding services: unconditional, on busy, on no reply and on not reachable. (Source: 3GPP TS 22.082 (ETSI), checked )
- No-reply forwarding waits 5 to 30 seconds, in 5-second steps; if the user never sets it, the carrier’s default applies. (Source: 3GPP TS 22.082 (ETSI), checked )
- Standard forwarding codes: 21 unconditional, 67 busy, 61 no reply, 62 not reachable, and 004 for all conditional kinds at once. (Source: 3GPP TS 22.030 (ETSI), checked )
- On a Verizon mobile phone, *72 plus a 10-digit number forwards calls, *71 forwards only unanswered calls, and *73 turns forwarding off. (Source: Verizon, checked )
The four kinds of call forwarding
The mobile standard that defines the feature, 3GPP TS 22.082, splits it into four services, each with its own service code in the companion standard for dial codes, 3GPP TS 22.030. Landlines and VoIP systems offer the same choices under other names.
| Kind | When the call is forwarded | Standard code |
|---|---|---|
| Unconditional | Always, whatever state your phone is in | 21 |
| On busy | You are already on a call, or you reject the call while it rings | 67 |
| On no reply | The phone rings for a set time and nobody answers | 61 |
| On not reachable | The phone is off, out of coverage, or not registered on the network | 62 |
Busy, no reply and not reachable are the conditional kinds, and the standard gives them a shared code, 004, so all three can be set in one step. While unconditional forwarding is on, the conditional settings stay stored but do nothing; switch unconditional off and they apply again. The standard also says the network gives you an indication that forwarding is active each time you make a call, one for unconditional and one shared by the conditional kinds. How that indication shows up depends on the phone.
What “call forwarding unconditional” means
Call forwarding unconditional is the name the standard gives the forward-every-call setting. While it is on, the network sends every incoming call to the other number whatever state your phone is in, so the call never rings your own phone, and you can still make calls as normal. On an iPhone, the Call Forwarding switch in the Phone settings is this setting, as how to forward calls on iPhone explains. If a phone reports it as active and nobody meant to set it, the forwarding guide has the codes that show and clear it.
How long before an unanswered call moves on
No-reply forwarding waits on a timer in the network. The standard lets that timer be set from 5 to 30 seconds, in steps of 5 seconds; if you never set it, the carrier’s default applies. The timer is what decides how many rings a caller hears before the handoff. Too long and callers hang up before anyone answers; too short and you cannot reach the phone in time.
How to turn it on and off
There are three common ways: a dial code typed on the phone, a switch in the phone’s settings or the carrier’s app, or a setting in the account page or admin panel of a landline or VoIP line.
The dial codes in the standard follow one pattern: the service code between a prefix and a closing #. For unconditional forwarding, **21*number# sets it up with the number to forward to, #21# switches it off, ##21# erases the stored number, and *#21# asks the network whether it is on. On no-reply forwarding a third field sets the timer, so **61*number**20# asks for 20 seconds.
Not every carrier uses those codes. On a Verizon mobile phone, for example, *72 plus the 10-digit number forwards your calls, *71 plus the number forwards only the calls you do not answer, and *73 turns forwarding off; Verizon notes that the confirmation tone can sound like a busy signal. The codes differ by carrier and sometimes by plan, so your carrier’s own support page is the authority for your line, and how to forward calls to another number goes through them carrier by carrier. Turning forwarding off is covered in how to turn call forwarding off again, so the change is easy to reverse.
Why it matters for a service company
Your business number is on the truck doors, the yard signs, the Google listing and years of invoices. Changing it is not an option, and neither is moving it away from the carrier that has served it fine. Forwarding is the way to keep that number exactly where it is and still decide who picks up. Moving the number to a new carrier is porting, a different job with its own paperwork, covered in how to port a business phone number.
The two modes suit different days. Unconditional forwarding is the right setting for a closed shop, a vacation, or a Sunday when nobody should be answering from the truck. Conditional forwarding is the everyday setting: the phone rings in your pocket first, and only the calls you miss go anywhere else.
On DispatchLine, you forward your business line to your DispatchLine number and the AI receptionist answers the calls that arrive; the forwarding guide has the steps.
Related terms
Sources: 3GPP TS 22.082 (the four forwarding services and the no-reply timer), 3GPP TS 22.030 (the dial codes) and Verizon’s call forwarding FAQs.
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