We have supported retail and restaurant point of sale systems for over 10 years and have garnered extensive experience with varied hardware and software packages. Below is a partial list of the hardware with which we have specific experience supporting.  (* indicates recommended hardware) 

Receipt printers - USB, Parallel, Serial, ethernet
  *Epson
  POS-X
  Star Micronics
  Samsung
  Cognitive
  Citizen
  Ithica
Barcode printers – Serial, USB, parallel
  * Zebra/Eltron
  Cognitive
  DataMax
  Epson   
Barcode readers
  * Symbol/ Metrologic
  * Honeywell
  POSX
  DataLogic
Magnetic Card Readers - Serial (RS232), USB connection, or Keyboard Wedge (PS2)
  * MagTek
  POS-X
  ID Tech
Cashdrawers – Manual, Printer driver, serial, and USB
  MMF
  APG
  MS-Cash
  POS-X
et cetera
  Touchscreens
  Pole Displays
  Dial up telephone modems
  Handheld computers
  Checkout scales
  Payment terminals