A card terminal needs almost no bandwidth. It will happily run on a connection too slow to load a web page. So when it keeps timing out, the problem is rarely speed, and chasing a faster line will not fix it. It is nearly always about which connection the terminal is using and how stable that connection is at the exact moment you are busiest. Here is how to work out which, and what to do about it.
The 30-second version
- Speed is almost never the problem. A transaction is a few kilobytes. Stability is what matters.
- Find out what your terminal is actually using first: its own mobile SIM, your Wi-Fi, or a cable. The fix is completely different for each.
- Terminals on guest Wi-Fi is the most common mistake we see, and it fails precisely when the room fills up.
- It happens at your busiest moment because that is when the airwaves are busiest, not because the terminal has chosen to be awkward.
- A terminal on its own SIM can still drop, usually because of where it is standing rather than the network.
- If payments stopping would stop you trading, the terminal needs a second route, not a faster first one.
On this page
First, which kind of terminal is it?
Nearly every argument about card machines goes wrong because nobody establishes this. The same symptom has three completely different causes.
| Type | How to tell | Why it usually drops |
|---|---|---|
| Its own mobile SIM | Works when your internet is down. Often shows a signal bar. | Poor signal where it lives, or a network issue. Nothing to do with your broadband. |
| Your Wi-Fi | Stops working when the Wi-Fi does. Had to be given a network and password. | Coverage, congestion, or being on the wrong network. The most common and most fixable. |
| Bluetooth to a base | A handheld that pairs with a station on the counter. | Range from the base, or the base itself losing its own connection. |
| A network cable | Plugged in and does not move. | Rare. Usually the cable, the port or the broadband itself. |
Worth checking before anything else
Pick up the terminal and look at what it says it is connected to. A surprising number of machines that were set up on a cabled or dedicated connection have at some point been moved onto the Wi-Fi by whoever was on shift when it was last reset.
How little bandwidth a terminal actually needs
A card transaction is a tiny exchange of data. A few kilobytes each way, over in a second or two. You could run a busy Saturday night on a fraction of the slowest business broadband we sell.
What a terminal will not tolerate is a connection that disappears mid transaction, or one where the response takes so long the terminal gives up and shows a timeout. Those are two different faults from slowness, and they are what you are actually experiencing.
This is why upgrading your broadband speed to fix card machine problems is usually money spent on the wrong thing. If the line drops for four seconds, it drops for four seconds whether it is 40Mb or 900Mb.
The guest Wi-Fi mistake
This is the single most common cause we are called about, and it is almost always well intentioned.
Somebody sets the terminal up and the easiest network to join is the guest Wi-Fi, because that is the password everyone knows. It works perfectly during the quiet afternoon when it was configured. Then service starts, sixty customers join the same guest network, and the terminal is competing with phones streaming video for the same airtime.
- Guest networks are often rate limited on purpose, which is sensible for guests and poor for payments.
- Many guest networks have client isolation and periodic forced reconnections, neither of which a terminal enjoys.
- Guest networks get the leftovers when the access point is busy, because that is what they are for.
A card terminal should be on a separate network from your customers, ideally its own, with its own name and password that staff do not hand out. On a properly built network that is a VLAN, the same approach we use to keep phones separated from everything else. On a simpler setup it can just be a second network name reserved for tills and terminals.
Why it fails when you are busiest
It feels personal. It is physics.
Wi-Fi is a shared medium. Every device in range takes turns, and when the room fills with phones the turns come round more slowly. A terminal that gets a clear slot instantly at three in the afternoon may wait long enough at eight in the evening to time out. Add the fact that a hundred bodies absorb a meaningful amount of 5GHz signal and the coverage that was fine when the room was empty is marginal when it is full.
It is also why the problem is so maddening to report. By the time an engineer visits on a Tuesday morning, everything works, because the conditions that caused it have gone home.
If you take one diagnostic note
Write down the time it fails and roughly how busy you were. A pattern of failures that cluster at your peak is a congestion or coverage problem. Failures scattered randomly through quiet periods point at the line or the terminal instead. That one observation saves a lot of guessing.
When the terminal has its own SIM
Terminals on their own mobile connection are not immune, they just fail for different reasons.
- Where it stands matters more than the network. A terminal that lives in a basement bar, behind a steel counter or next to a fridge may be in the one spot with no usable signal.
- It is locked to one network. A standard terminal SIM uses a single mobile network. If that network is weak at your postcode, it is weak all day, every day. A multi network SIM can use whichever is strongest instead, which is exactly the problem it was designed for.
- Older terminals on 2G. Some long serving card machines still fall back to 2G, and the networks are switching that off over the next few years. Our guide on the 2G switch off lists the dates and what to check.
Fixing it properly
- Establish what it is connected to, using the table above. Everything else depends on this.
- Get it off the guest network if that is where it is. Give tills and terminals their own network that customers never see.
- Check coverage where it actually stands, not where the router is. If the signal is marginal when the room is full, an access point in the right place fixes it permanently.
- Give it a second route if payments are critical. A terminal on Wi-Fi backed by a mobile connection, or a site with automatic failover, keeps taking money when the main line goes. For most hospitality and retail businesses this is the one that pays for itself.
- Log the failures for a week. Time and how busy. If you then need to call anyone, that log is worth more than any description of the symptom.
Payments dropping at the worst possible moment?
Tell us what the terminal is connected to and when it fails. We will tell you honestly whether it is coverage, congestion or the line, and what it would take to make it stop. We have done it for plenty of bars, restaurants and garages around Merseyside.