A cash drawer contains no processor and no software. It is a solenoid, a latch and a spring, plus a switch that tells the printer whether the drawer is shut. It opens when the printer sends a short voltage pulse down a two-wire cable, and it does nothing at all if the voltage or the wiring is wrong.
That is the whole mechanism, and it explains almost every “the drawer will not open” ticket we see. The fault is rarely the drawer and rarely the printer. It is the pairing.
The drawer is a solenoid, not a computer
When a sale completes, the POS software sends an ESC/POS command to the printer. The printer drives its kick-out port, which is a 6-pin modular jack, and the solenoid in the drawer pulls the latch for a fraction of a second. The spring pushes the till out.
Two consequences follow immediately. First, the drawer depends on the printer being alive — if the printer is offline, the drawer stays shut even though the sale went through. Second, the drawer has no way to report a fault: it either moves or it does not.
12 V and 24 V are not interchangeable
A 12 V solenoid on a 24 V port gets roughly four times the power it was designed for. It opens hard, buzzes, and the coil runs hot enough to deform the former over a few months. A 24 V solenoid on a 12 V port gets a quarter of its rated pull: the latch twitches, sometimes releases, and increasingly does not.
This is why the model number matters more than the brand. The POS-410A is a 12 V unit on RJ11. The POS-410B accepts 12 V or 24 V on RJ11 or RJ12, which makes it the safe choice when the printer model is not yet decided.
If a drawer “sometimes” opens, check the voltage pairing before replacing anything. A drawer that opens on the first sale of the morning and not later in the day is usually a supply sag, not a solenoid.
The cable: RJ11, RJ12 and the pins that matter
The connector is a 6-position modular jack, and the pulse rides on the two centre conductors. Three things go wrong with the cable:
- A telephone cord. A 4-position phone cable physically fits the jack and carries no current on the right pins. It is the most common wrong part in the drawer box.
- RJ11 versus RJ12. Same shell, different contact count. A 6P4C plug in a 6P6C socket can leave the sense line open, so the printer reports the drawer as open when it is shut — or never reports it at all.
- Length and routing. The cable runs from the printer to the drawer, often along the same tray as mains wiring. A long run next to a power cable picks up enough noise to trigger a spurious pulse.
Keep the original cable. When one is lost, replace it with a 6P6C drawer cable of the same length rather than the nearest phone lead in the IT box.
When the drawer is plugged into the PC
It never opens, and the reason is structural: a PC has no kick-out port. Some installations run the drawer cable to a USB-to-serial gadget, or to a drawer interface box, but the standard path is printer to drawer.
The exception is a drawer with its own USB or RS232 interface and a separate 12 V supply. The POS-350A takes USB or RS232 plus a 12 V DC adapter, which is the arrangement that works when the site has an Android terminal with no printer attached.
Mechanical duty is a real spec
Drawers fail mechanically far more often than electrically, and the numbers to compare are straightforward:
- Opening time: 0.3 s is the current commercial standard. Slower feels broken at a busy counter.
- Cycle rating: the POS-410A is rated past 1,000,000 open-and-close cycles.
- Noise: slide-rail designs come in under 50 dB. A drawer that clacks across a quiet bar is a customer complaint, not a spec detail.
- Bill capacity: 600+ notes on the POS-410B and the POS-350A, which matters at a site that only banks once a week.
Footprint is fixed across the range at 410 x 420 x 100 mm, which is the size that fits a standard counter cut-out and takes a 4B, 5B or 8C till insert depending on the currency.
Coin and note layout is not cosmetic. A drawer laid out for a currency with high-denomination notes and few coins is wrong for one where small coins dominate, and the cashier pays for that in seconds per transaction for the life of the counter.
Comparison
| Specification | POS-410A | POS-410B | POS-350A |
|---|---|---|---|
| Kick-out voltage | 12 V | 12 V / 24 V | n/a — USB/RS232 + 12 V adapter |
| Connector | RJ11 | RJ11 / RJ12 | USB or RS232 |
| Till layout | 4B / 5B / 8C | 4B / 5B / 5C / 8C | Standard insert |
| Opening time | 0.3 s | 0.3 s | 0.3 s |
| Footprint | 410 x 420 x 100 mm | 410 x 420 x 100 mm | Compact |
| Use when | Printer is known to be 12 V | Printer voltage not yet fixed | No printer on the terminal |
The till insert is where cashiers lose seconds
The mechanism opens the drawer. The insert decides how fast the cashier works once it is open, and it is the part buyers spend the least time on.
The designations 4B, 5B and 8C describe the layout: four or five note compartments, and eight coin compartments. Which one is correct follows the currency, not the store size. A market where the highest circulating note is large and coins are low-value wants more note sections and a deep coin tray. A market dominated by small notes and heavy coin use wants fewer note sections and more coin divisions, because sorting coins is the slow part of a cash transaction.
A removable insert matters more than it looks. It lets a cashier carry the till to a back-office counter for counting without moving the drawer body, and it lets a site swap the whole insert at shift change. Drawers with a fixed insert get used with a loose cash tray on top, which is how notes end up under the slide rail.
At a busy lane the difference between a well-matched insert and a generic one is a second or two per transaction. Across a day that is the reason our retail counter configurations specify the insert alongside the drawer rather than as an afterthought.
Three installation mistakes we see repeatedly
Bolting through the slide rail. A drawer has to be fixed down, or it walks across the counter every time it opens. Fixing it through the rail instead of the case body is the fastest way to seize the mechanism, and it looks identical from above.
No clearance behind the unit. The till travels forward when it opens. A drawer set hard against a back panel or a cable bundle opens halfway, and the operator assumes the solenoid is weak. Leave the travel distance clear, plus room to reach the release lever if there is one.
The cable routed through the drawer body. The kick-out lead gets zip-tied to the drawer when the run is short, so it flexes every time the drawer opens. It fails at the connector after a few months, and the symptom is intermittent opening that gets diagnosed as a printer fault. Route it to a fixed point on the counter, then to the drawer.
All three are installation issues, not product issues, and all three present as “the drawer is broken”. The step-by-step counter setup in our cashier machine walkthrough covers the sequence that avoids them.
Drawers, printers and scanners are catalogued together in the POS peripherals range, because the three have to be chosen as a set — the drawer is only as good as the printer driving it.
Setup checks before you call it a fault
In order: confirm the drawer voltage matches the printer port; confirm the cable is 6P6C and not a phone lead; run the printer self-test, which usually fires the port once; and check that the software is actually sending the pulse rather than only printing a receipt. Four checks, in that order, resolve most tickets without a return.
Questions we get
Can the drawer open without a printer?
Only if it has its own interface. A drawer with a USB or RS232 board and a 12 V supply can be driven directly; a plain RJ11 drawer cannot, because the pulse has to come from somewhere.
Why does my drawer open at random?
Three usual causes: a driver sending the pulse twice, a shared COM port with another device, or electrical noise on a long cable routed beside mains. Start by moving the cable, then test with the printer disconnected from the network.
Does the drawer work with an Android POS terminal?
Yes, when the terminal has a kick-out port or the drawer has its own USB/RS232 interface. Most Android all-in-ones with a built-in printer expose the port on the printer, so the standard printer-to-drawer cable still applies.
