POS Hardware Cheatsheet
POS Hardware Cheatsheet
Receipt printers, scanners, cash drawers, and card terminals at a glance.
Receipt Printers
| Thermal (no ink) | Heat-sensitive paper ߀” no cartridges needed; most common type |
| 80 mm paper width | Standard POS paper roll; 58 mm used for smaller/mobile printers |
| ESC/POS protocol | Standard command set for printer control (Epson originated, industry-wide) |
| USB / Ethernet / Serial | Connection options ߀” Ethernet for shared/networked printers |
| DK (Drawer Kick) port | RJ11/RJ12 port on printer that triggers the cash drawer via voltage pulse |
Barcode Scanners
| 1D laser scanner | Reads linear barcodes (EAN-13, UPC-A, Code 128) ߀” fastest for retail |
| 2D imager | Reads QR codes, Data Matrix, PDF417 in addition to 1D barcodes |
| HID keyboard emulation | Scanner acts as keyboard ߀” no driver needed; sends barcode as keystrokes |
| COM port / serial mode | Used when POS software reads a serial port directly |
| Suffix character | Usually Enter (\r\n) after barcode ߀” configurable via programming barcode |
Cash Drawers
| DK cable (RJ11) | Connects drawer to DK port on receipt printer |
| Trigger via printer | POS sends ESC/POS open-drawer command to printer; printer pulses the drawer |
| USB drawer controller | Alternative to printer-triggered opening; less common |
| Spring tension | Worn springs cause slow/incomplete opening ߀” replace spring or full drawer |
Card Terminals
| Integrated | POS controls terminal directly via SDK/API ߀” tightest integration |
| Semi-integrated | Terminal on local network; POS sends amount, terminal reports result |
| Standalone | Independent device; staff manually enter amount ߀” no integration |
| PCI DSS compliance | Card terminals must be on the approved PTS device list; firmware updates required |
| Common vendors | Verifone, Ingenico, PAX, Castles ߀” each has their own SDK/protocol |