Conditional call forwarding for small business, explained
Conditional call forwarding moves a call on only when nobody answers or the line is busy. Which type a trade firm needs, how long to ring, where calls go.
An electrician is halfway up a ladder with a light fitting in one hand. The office phone rings in an empty office. A while back he set every call to forward to his mobile, so now the mobile buzzes in his pocket instead, and he can't reach it either. The caller hears it ring out and tries the next firm.
Forwarding everything to one mobile moves the problem from the desk to the van. Conditional call forwarding works differently. The phone rings where it always rings, and the call moves on only if a condition is met: nobody picks up, the line is busy, or the mobile has no signal. When someone is in the office, nothing changes. When nobody is, the call goes somewhere that can answer it.
This guide covers the four conditions, how long to let a phone ring first, how to set it up on a mobile and on an office line, and where the calls should end up. I checked every code and menu name below against the vendors' own help pages on 5 October 2026: Apple, Google, AVM and Deutsche Telekom. Carriers differ, so treat the codes as examples and confirm yours on your own network's help page.
The four kinds of forwarding
Phone networks and office systems mostly offer the same four options, under slightly different names.
- Always. Every call goes straight to the other number and your phone does not ring. This is the unconditional one.
- No answer. Your phone rings for a set time, then the call moves on. Some systems call it "no reply" or "delayed".
- Busy. The call moves on only while you are already on another call.
- Not reachable. For mobiles. The call moves on when the phone is off or has no signal.
A trade business that sometimes has someone in the office wants "no answer" and "busy" together. "Not reachable" is worth adding on a work mobile, because a roof, a cellar or a new-build with no signal is a normal working day. "Always" is for the two weeks in August when the workshop is shut.
How long it should ring first
This is the setting that decides whether the forwarding helps. Too short, and the call leaves before anyone in the office can reach the desk. Too long, and the caller gives up before it moves on.
Some systems give you a fixed choice. AVM's FRITZ!Box, a router common in Germany, offers "Delayed", which forwards after 20 seconds, and "Long delay", which forwards after 40. On mobile networks you can often pick the time yourself. Deutsche Telekom's published code list allows 5 to 30 seconds in steps of five. Google's help for its Phone app says many carriers let you change how long a phone rings before calls go to voicemail, and sends you to the carrier to do it.
As a rule of thumb, if someone is at the desk most mornings, give them 15 to 20 seconds. If the office is empty most of the day, keep it short, around 10 seconds. Ringing an empty room for longer only adds to the caller's wait.
Setting it up on a mobile
On an iPhone. Apple's guide puts call forwarding under Settings > Apps > Phone > Call Forwarding, where you turn it on and enter a number under Forward To. That switch forwards every call, and your iPhone stops ringing. For forwarding when the line is busy or not in service, Apple tells you to ask your carrier how to set it up.
On Android. Google's Phone app help also points to the carrier for the ring time before forwarding. There is no single Android menu to rely on.
The codes that work on both. Conditional forwarding is usually switched on by dialling a short code in the phone's keypad and pressing call. Google's Voice help describes it this way and gives AT&T as an example:
| Condition | AT&T code, from Google's help |
|---|---|
| No answer | *61*number# |
| Not reachable | *62*number# |
| Busy | *67*number# |
Deutsche Telekom publishes its own versions with two stars at the front: **61*number# for no answer, **61*number**20# to forward after 20 seconds, **62*number# for not reachable, **67*number# for busy and ##61# to turn no-answer forwarding off. The pattern is similar from one network to the next, but the exact codes are not. Google warns that codes vary by carrier, and that some carriers which resell another network's service may not offer conditional forwarding at all. So look up your own network's page before you dial anything.
One safety point. Apple says the iPhone alerts you and blocks links in messages, emails, webpages and apps that ask you to turn on call forwarding, because scammers may use them. Only set forwarding up yourself, to a number you know.
Setting it up on an office line
On a desk phone or router the same options usually sit in the settings menu. On a FRITZ!Box, AVM's help gives the path as Telephony > Call Handling > Call Diversion > New Call Diversion. There you pick which calls to divert, where they go, and the type: Immediately, Delayed, Long delay, When busy, or Parallel call, where both phones ring at once.
There is a detail in AVM's help worth knowing. For a diversion to an outside number, the box first tries to set it up in the provider's exchange. If that doesn't work, the box diverts the call itself, and AVM lists two simultaneous connections on that number as a requirement. With a hosted phone system, check the provider's portal or help pages for the same choices.
Where the calls should go
Forwarding is only as good as what answers at the other end.
Voicemail. Cheap, and it catches the callers who leave a message. The trouble is the ones who don't. The one-week missed-call audit shows you how many callers hang up without a word.
A colleague's or your own mobile. A person answers, if they can. On a ladder or under a sink they often can't, and if that mobile has its own voicemail switched on, the call ends up there instead of on the office system. Check the cost as well. Deutsche Telekom says forwarding to its own voicemail is free and forwarding to other numbers may cost extra depending on the tariff, and other carriers set their own rules.
An answering service or an AI receptionist. Both pick up every time. They differ in what happens next, and in how they are priced. The comparison of an AI receptionist vs an answering service sets them side by side.
Forwarding to an AI receptionist
An AI receptionist that works through forwarding has a phone number of its own. You point your no-answer and busy forwarding at that number, using whichever method above fits your line. Two settings matter more than the rest.
- Ring time. Short enough that callers stay on the line, long enough that someone in the office can still pick up first. If the office is staffed in the mornings only and your system can switch forwarding on a schedule, use that.
- Busy as well as no answer. Without it, the second caller during a long phone call hears an engaged tone.
In the EU the receptionist has to tell callers they are talking to an AI from the start of the call, under Article 50 of the AI Act, which applies from 2 August 2026. Our AI receptionist says so in its first sentence, asks for the caller's name, address, callback number and what the job is, and can book a slot in your calendar. You get a written summary of each call.
Test it before a real customer does
- Call your business number from a phone that is not the forwarding target.
- Don't answer, and time how long it takes to move on.
- Listen to what the caller hears at the other end.
- Test busy too. Stay on one call and ring the number from a second phone.
- Write down how to turn forwarding off, so whoever covers your holiday can change it.
Then check your missed-call list a week later. Any call that still rang out with no answer shows you the gap that's left.