SCANTECH ID (Champtek company) Discovery SG-20 - Manual (Page 117)

Scantech-ID Discovery SG-20 109
What is the difference between RS-232, RS-422 and RS-485, while talking about
the SG-20?
RS-232. The most simple, single unit configuration, full duplex, 4 wires +
ground, maximum distance between the Back Office and the terminal: 15
meters.
RS-422. Single unit configuration, full duplex: sending and receiving data
simultaneously. (in practice: 4 data wires/ crossed) max. distance 1200
meters.
RS-485. Multiple unit network configuration, half-duplex: sending and
receiving on the same two lines, but not simultaneously, (in practice: 2
wires/straight, a driver is necessary to control data traffic) max. distance
1200 meters.
See also the document “SG-20 Discovery Configurations Quick Reference.PDF”.
H-5 NETWORKING
Which type of network should I choose?
For a network of max. 32 units you can use RS-485. Your network will be more or
less dedicated for the Discovery’s. (Under certain conditions also your existing
SG-10’s may share this network).
Ethernet using TCP/IP is required if you want to connect more than 32 units (now
or in the future) or if you want to use the existing network infrastructure. The
required length of new cabling might be much shorter than with other
cablingtypes and if you use an existing infrastructure you gain lots of flexibility.
What’s the advantage of RS-485?
It is an industrial standard, it controls data transmission, is more resilient and has
a higher data security than RS-232. In addition: Once chosen for the RS-485
configuration, expanding the number of SG-20 terminals per store is very easy!
What’s the advantage of Ethernet TCP/IP?
Above the advantages it has higher performance, can be expanded “without any
limits” and can use existing ethernet infrastructure. Since the same cabling may
be used for computers, checkouts, telephones and Discovery’s you are very