Hardware Types & Cables
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SELLmatix supports an almost infinite range of Point of Sale hardware devices, and while the most common device have configuration screens available from the Tools Menu, almost any device can be configured and used through advanced configuration options.

Input Devices
Send data to the computer, and in most cases this is one way, because the computer never sends data to the device. Examples include:-

  • Barcode Scanners
  • Magnetic Card Readers
  • Keyboards
  • Touch Controllers for Touch Screens
Output Devices
Receive data from the computer, and in most cases this is also one way, because they never send data to the computer. Examples Include:-

  • Computer Displays
  • Customer Pole Displays
  • Printers
  • Cash Drawers
Two Way Devices
These devices both send and receive data from the computer. Such devices are relatively rare, but an example is:-

  • Electronic Scales. When the computer needs to read a weight it sends data to the scale asking for the weight, and the scale responds.
Connections
Each of these devices connects to the computer using a "port" and a cable. The most common types of "port" are:-
  • Serial
  • Parallel
  • USB
  • Keyboard
  • TCP/IP Network Connection
Every device can use a different type of port, but you cannot mix the port types for a particular connection. In other words, if you have a serial scanner, it must use a serial cable and connect to a serial port on the computer. But that does not stop you using a parallel connection for a printer.

On the computer, you do need to have one serial port for each serial device used, and one parallel port for each parallel device.

USB ports allow you to use a USB "hub" so that the USB hub plugs into one USB port on the computer, and more than one USB device plugs into the USB hub.

There is only ever one keyboard port on the computer, and other devices that use the keyboard port are generally connected in series. If a "keyboard wedge" barcode scanner is used, then the keyboard plugs into the scanner, and the scanner plugs into the computer.

Parallel Ports
Have the following features:-

  • Data flow is mostly one way... From the computer to the device. The ability for the device to send data to the computer is very limited (read nonexistant) in POS applications.
  • Cable length is limited. 5 meters is really pushing it.
  • Data transfer rates are quite fast.
  • Parallel interfaces are mostly used for printers.
Serial Ports
Have the following features:-

  • Data flows in both directions equally well.
  • Cable length can be from a few inches up to 100 meters (or more)
  • Data transfer rates are quite slow, and as the cable length increases, the speed must be reduced. A graphics printer using a 50m serial cable is like watching the grass grow.
  • Serial interfaces are the most flexible. They are typically used for barcode scanners, Mag stripe readers, Customer Pole Displays, printers, modems, cash drawers, electronic scales etc. Almost anything.
Serial connections are the oldest, most flexible and reliable types of interface. With that flexibility comes a degree of complexity in making up cables. For further information, please refer to Debugging Serial (RS-232) Cables

USB Ports
Have the following features:-

  • Data flows in either direction equally well
  • Cable length is limited to around 15 meters
  • Data transfer rates are very good.
  • The cost of devices with USB interfaces is often a little higher than serial or parallel
  • These devices are relatively new, and some early models were not as reliable as serial and parallel interfaces.
Keyboard Wedges
Have the following features:-

  • Data flows only from the device to the computer
  • Cable length is limited to 3-4 meters
  • Data transfer rates are quite slow. (Slightly faster than you can type)
  • These devices cannot be "hot plugged", and the computer must be powered down to connect or disconnect these devices, otherwise hardware damage may occur.
  • Many new POS configurations with Touch Screens do not use keyboards at all, and some keyboard wedge devices will not work without a keyboard.
  • These interfaces are generally used for input devices such as barcode scanners or magnetic card readers.
TCP/IP Network Connections
These are normally used to connect computers rather than POS devices, however where there is a long distance between the computer and a kitchen or bar printer, TCP/IP "Print Servers" are often used. These are small boxes connected to the network by cable or WiFi connection, which have Parallel or Serial ports into which the printers are connected. These devices are quite low in cost, and work very well for fast printing at a long distance.

Further Information
Additional information is available about:-

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