Payment terminals and business lines

Last reviewed: 2026-03-04

Which business devices are affected

Any device in your business that dials out over the phone line may be affected by the switch to digital voice. Common examples:

• Card payment terminals, older PDQ machines that process transactions over the phone line (you can usually hear them dialling)
• Fax machines, still used in some medical practices, legal offices, and businesses for signed documents
• Franking machines, some models download postage rates via the phone line
• EPOS systems, electronic point-of-sale systems that use a phone line for transaction processing or stock updates
• Monitored alarm systems, burglar alarms, fire alarms, or CCTV that dial out to a monitoring centre (covered in detail in our security and fire alarms guide)
• Auto-attendant or IVR systems, "press 1 for sales" phone systems that may use ISDN or analogue lines

Card payment terminals

If your card machine dials over the phone line (you hear a modem-like sound during transactions), it will likely stop working after the switch. Dial-up card machines are already being phased out by payment processors.

Replacements use mobile data (GPRS/4G) or connect via your broadband. Contact your payment provider and ask for a replacement. Most providers have been issuing new terminals for some time, often at no extra cost on existing contracts.

Do not leave this until the last moment. If your card machine stops working, you cannot take card payments.

Fax machines

Fax over digital voice is unreliable. The analogue fax protocol (T.30) does not work consistently over VoIP connections. Some calls may go through; others will fail partway or produce garbled output.

Options:

• Online fax services, which let you send and receive fax via email or a web interface. No phone line needed.
• Fax-to-email, where some providers offer a virtual fax number that delivers incoming faxes as email attachments.
• Replace with email or secure file transfer where the recipient agrees.

If you are in a sector that requires fax (some NHS and legal workflows), check with your compliance team about approved alternatives.

Franking machines

Franking machines that download postage rates via the phone line will need to be updated. Most modern franking machines can connect via broadband or Wi-Fi. Contact your franking machine supplier and ask about a network-connected update or replacement.

Business phone systems (PBX, ISDN)

If your business uses a PBX (private branch exchange) connected to ISDN or analogue trunk lines, those lines will be retired along with the PSTN. You will need to move to a SIP trunk or a hosted VoIP phone system.

This is a larger project than a simple handset swap. Talk to your telecoms provider or IT support well in advance. Migration of business phone systems can take weeks to plan and implement.

Reception and trade counter phones

Some businesses use a standalone analogue phone at a reception desk, trade counter, or warehouse that connects directly to the PSTN rather than through a PBX. If that phone is plugged into a wall socket, it will need to be moved to the broadband router's phone port after migration, or replaced with a SIP handset or mobile if the business has already moved to a hosted VoIP system.

What to do

1. List every device in your business that uses the phone line. Include things you might not think of: alarm panels, door entry, building management systems.
2. Contact each supplier or service provider. Ask whether the device is compatible with digital voice and what the replacement or upgrade path is.
3. Prioritise by business impact. A card machine that stops working costs you revenue immediately. A franking machine can be worked around temporarily.
4. Test after migration. Once your phone line is moved, test every device. Do not assume they will all work. Test each one individually.