Recommended Cable Type And Permissible Length; Check Point During Installation; Termination Resistor - IDTECK Star LX505 User Manual

7.1.2 Recommended Cable Type and Permissible Length

Reference
1
2
3
Door Lock, Alarm Device
4
5
6
+
: Thicker wires are needed if you connect the reader with high current consumption.

7.2 Check Point during Installation

7.2.1 Termination Resistor

Termination resistors are used to match impedance of the network to the impedance of the
transmission line being used. When impedance is mismatched, the transmitted signal is not
completely absorbed by the receiver and a portion of signal is reflected back into the
transmission line. The decision whether or not to use termination resistors should be based on
the cable length and data rate used by the communication system.
For example, if you use 9,600 baud rate and 1,200m length of cable, the propagation velocity of
cable is 0.66 x speed of light (This value is specified by the cable manufacturer), if we assume the
reflections will damp out in three round trip up and down the cable length, the transmitted signal
will stabilize 18.6us after the leading edge of a bit. Since the data bit is captured in the middle of
the bit which is approximately 52us after the leading edge of a bit. The reflection stabilizing time
18.6us is much before the center of the bit therefore the termination resistors are not required.
However, if you install the cable to maximum length, the impedance of cable and network is
mismatched and the transmitted signal is overlapped by the reflected signal. In this case, it is
recommended to add termination resistors to the end of the receiver lines. A 120Ω resistor can
Description
LX505 Power (DC12V)
DC Power -> LX505
Reader
(Power and Data)
Exit Reader -> RF20
Door Contact
Exit Button
Sensor Input
Input -> LX505
Lock (Alarm) -> LX505
RS232 Cable
Converter -> Host P.C.
RS485 Cable
LX505 -> LX505
LX505 -> Converter
Cable
Specification
Belden #9409,
18 AWG
2 conductor, unshielded
Belden #9512,
22 AWG
4 conductor, shielded
Belden #9514,
22 AWG
8 conductor, shielded
Belden #9512,
22 AWG
4 conductor, shielded
Belden #9514,
22 AWG
8 conductor, shielded
Belden #9409,
18AWG
2 conductor, unshielded
Belden #9829,
24 AWG
2-twisted pair, shielded
Belden #9829,
24 AWG
2-twisted pair, shielded
14
Maximum
Distance
30m
150m
300m
300m
15m
1,200m