Winter is the season when businesses are tested not by competitors but by outage schedules. A customer calls, hears "the number is unavailable" — and a minute later dials another number from Google. This checklist covers everything you need to do before the first blackouts so your company number keeps answering even when the office is dark.
Why phones "go down" together with the power
Most companies lose calls during outages not because of their provider, but because of one weak link nobody thought about in advance. The typical picture looks like this:
Closing at least two of the three links is enough to keep the company reachable. Close all three, and customers won't even notice you have an outage.
The main rule: telephony shouldn't live in the office
If your PBX is a box in the server room, it works exactly as long as the socket (or UPS) does. A cloud (virtual) PBX works differently: numbers, voice menu, queues, forwarding rules and call recordings live on the provider's servers, not on your premises. The office can be completely without power — and the company number keeps taking calls and routing them to wherever there are people and a connection.
| What happens during an outage | Office (analog/on-premise) PBX | Cloud PBX |
|---|---|---|
| Does the number take calls | No, unless there is backup power | Yes, servers run independently of the office |
| Voice menu (IVR) | Switches off together with the PBX | Works and can announce your schedule |
| Forwarding to mobiles | Only via the carrier line, often paid and complicated | Set up in your account in a few minutes |
| Managers working from home or a shelter | Practically impossible | Via an app on a smartphone or laptop |
| Call recording and statistics | Calls that bypassed the PBX are lost | Stored in the cloud no matter where the call was answered |
Most often, people call us on the first day of outages asking "why isn't the telephony working?". But the telephony is working — it's just that all the calls are going to IP phones in a dark office. The rule for winter is simple: every call needs a backup route to a mobile phone, and it has to be set up in autumn, not when the lights have already gone out.
Where to take calls without power
A cloud PBX settles the question "will the number take the call". What remains is "where will the call go". Here are the main options — from most to least dependent on electricity:
| Device | What it needs to work | Without power | Best for |
|---|---|---|---|
| Desk IP phone | A socket or PoE switch + internet in the office | Only with a UPS | Reception, call center in normal mode |
| Stream Phone on a laptop | A charged laptop + Wi-Fi or mobile internet | A few hours on battery | Managers who work in a CRM |
| Stream Phone on a smartphone | 3G/4G mobile internet | Yes, while the mobile network is up | Anyone who needs to work from anywhere |
| Forwarding to a mobile number ("Mobile Employees" service) | GSM coverage only, no internet needed | Yes, the most resilient option | Executives, on-duty staff, field managers |
The most reliable setup is a combination: primary route to the app, backup route to a mobile number.
Install Stream Phone on the smartphones of everyone who takes calls before the outages start. The app shows incoming calls to the company number, not the employee's personal number — the customer can't tell where they were answered from.
Why you shouldn't rely on mobile internet alone
During long outages, mobile operators' base stations switch to batteries and generators. They usually last several hours, but in some areas the connection may degrade or drop. That's why you need a second route: if the app fails to take the call, the PBX automatically forwards it to a regular mobile number over GSM, which doesn't need the internet.
Backup internet and power: how much you need
If the team stays in the office (you have a generator, a power station or a shelter with sockets), the internet needs preparing too. There are two common setups.
Fiber (GPON) + UPS for the router
A GPON fiber network is passive on the stretch to your office — it doesn't need power in the building's stairwell. So the internet stays up as long as you power two devices: the optical terminal (ONT) and the Wi-Fi router. Together they draw roughly 10–20 W, so even a small UPS or a power bank with a 12 V cable keeps them running for several hours.
A 4G router as a backup channel
If your provider isn't on GPON, keep a 4G router with a SIM card from a different operator than most of your employees use. When the main channel drops, connect to it — and IP telephony keeps working.
| Equipment | Consumption (approx.) | 20,000 mAh power bank | ~500 Wh power station |
|---|---|---|---|
| Router + optical terminal | 10–20 W | 2–4 h | 18–30 h |
| 4G router | 5–10 W | 4–8 h | 35–60 h |
| IP phone (PoE) | 3–6 W per unit | — | depends on the number of units |
| Laptop during calls | 30–60 W | 1–2 charges | 8–12 h |
Approximate figures, accounting for voltage conversion losses. Check the exact numbers on the device label or in the power adapter specs.
Don't plug the router into the UPS via the same extension cord as a heater or kettle. An overloaded UPS shuts down exactly when you need it most.
We'll connect a cloud PBX free for 14 days, set up backup routes to mobiles and run a test outage together with you.
Checklist: what to set up in advance
Go through the items and tick off the ones you've done. Most take under 10 minutes, and together they close all three weak links.
- Move the company number to a cloud PBXIf your number is currently tied to an office PBX or an analog line, move it. The number your customers know stays the same.
- Set up forwarding on no answerIf an employee doesn't answer their extension within 15–20 seconds, the call automatically goes to their mobile.
- Create a "Blackout" group2–3 people in charge with mobiles who receive the call if the whole queue is unavailable.
- Prepare a voice greeting for outagesFor example: "We're working as usual, connecting you to a manager." Record it in advance and turn it on with one switch.
- Turn on missed-call notificationsIn Telegram, by email or in your CRM — so no call that wasn't picked up gets lost.
- Install Stream Phone on smartphones and laptopsMake sure everyone can log in with their own credentials and make a test call.
- Enter up-to-date mobile numbers in the PBXDouble-check with the team: an outdated number in the forwarding rules is the most common reason for "lost" calls.
- Give power banks to everyone on the lineAt least 10,000 mAh per person — enough for a full working day of calls.
- Agree on a duty scheduleWho takes calls if an outage coincides with lunch or the end of the working day.
- Connect the router and optical terminal to a UPS or power stationSeparately from heaters and household appliances.
- Have a backup 4G router or a SIM card from another operatorAnd make sure it has an active plan with internet.
- Write down the backup router's Wi-Fi password somewhere easy to findSo you don't have to hunt for it with a flashlight.
- Check that the CRM is accessible from a phoneA manager taking a call from home needs the customer card, not just a voice.
- Prepare an SMS or Viber message templateFor when you need to warn customers about schedule changes or delivery delays.
- Add a callback widget to your websiteThe customer leaves their number, and the PBX connects them to the first available manager as soon as one is back online.
How to test everything before outages
Setting things up is only half the job. The other half is making sure the setup actually works. The best way is to stage a controlled "blackout" during working hours, while your provider's support is available.
- Switch off the circuit breaker in the office (or at least unplug the IP phones and router).
- Call the company number from your personal mobile — and see which device rings.
- Don't answer on the first device — check that forwarding to the mobile kicks in after 15–20 seconds.
- Turn off mobile data on the smartphone — check that the call still comes through over GSM.
- Miss a call completely — make sure the missed-call notification arrives.
- Open statistics and call recordings in your account — all test calls should be there.
Employees change numbers, leave, upgrade their phones. A setup that worked in October may have a "hole" by January. 15 minutes of testing once a month costs less than one lost major customer.
FAQ
Will the cloud PBX work if the whole city is without power?
Yes. Stream Telecom servers are located in Tier 3 data centers with their own backup power and backup communication channels. An outage in your office or district doesn't affect them — the only question is which device the call goes to.
Does the customer pay more if the call is forwarded to a mobile?
No. The customer calls your usual number and pays according to their own plan. Forwarding happens inside the PBX, and its cost depends on your plan.
What if both power and mobile coverage go down?
The cloud PBX will still take the call: play a voice message, offer to leave a request or log the number in the missed-call list. As soon as the connection is back, the manager will see whom to call back and won't lose anyone.
How long does switching to a cloud PBX take?
A basic connection with a number takes from one day. Porting an existing number from another operator takes longer, but in the meantime you can work on a temporary number with forwarding, so no calls are lost.
- Move telephony from the office to the cloud so your number doesn't depend on a socket.
- Set up two routes for every call: the app + a mobile number.
- Give the router and optical terminal backup power.
- Run a test outage and repeat it every month.
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