User's Manual

Calculating Maximum Wiring Lengths
apC/8X Technical Manual C-3
Determining Wiring Ranges
To calculate wiring ranges, you need to know:
 Wire type used to connect the RMs to the apC/8X
 Resistance (ohms per foot) based on the wire type
 Number and type of readers on the chain.
 Distances between each element (reader) in the chain
Wire Types and Resistance
The following table lists the resistance (ohms per foot) for common wire
types.
Current Draw for Readers
The following table lists the current draw for RM4 and RM4E readers.
Diagram of apC8X and Readers
Figure C.1 shows a sample diagram of an apC/8X and RM4/4E readers on the
chain. As shown in the diagram, the three readers are laid out as follows.
 Reader A is 50 ft. from the apC/8X
 Reader B is 500 ft. from Reader A.
 Reader C is 250 ft. from Reader B.
Table C.1: Wire Types and Resistance
Wire Type Resistance (ohms per foot)
18 AWG 0.00879
22 AWG 0.002340
24 AWG 0.03600
Table C.2: Wire Types and Resistance
Reader Type Current Draw
RM4 75 mA (round up to 100 mA or .1A)o
RM4E 175 mA (round up to 200 mA or .2A)