Installation guide

7800 Series Keypad Installation Guide 19
Wiring Specications for Keypad Bus
When planning a keypad bus installation, keep in mind the following specications:
1. DMP recommends using 18 or 22-gauge unshielded wire for all keypad and
LX-Bus circuits. Do Not use twisted pair or shielded wire for LX-Bus and keypad
bus data circuits. To maintain auxiliary power integrity when using 22-gauge
wire with a Model 7872 or 7873 do not exceed 225 feet. When using 18-gauge
wire do not exceed 500 feet. Install an additional power supply to increase the
wire length or add devices.
2. Maximum distance for any one circuit (length of wire) is 2,500 feet regardless
of the wire gauge. This distance can be in the form of one long wire run or
multiple branches with all wiring totaling no more than 2,500 feet. As wire
distance from the panel increases, DC voltage on the wire decreases.
3. Maximum number of devices per 2,500 feet circuit is 40.
Note: Each panel allows a specic number of supervised keypads. Add
additional keypads in the unsupervised mode. Refer to the panel installation
guide for the specic number of supervised keypads allowed.
4. Maximum voltage drop between the panel (or auxiliary power supply) and any
device is 2.0 VDC. If the voltage at any device is less than the required level,
add an auxiliary power supply at the end of the circuit. When voltage is too low,
the devices cannot operate properly.
Refer to the LX-Bus/Keypad Bus Wiring Application Note (LT-2031) for more
information. Also see the 710 Module Installation Sheet (LT-0310).
Keypad Specications
MODEL NORMAL/
STANDBY
CURRENT
ALARM
CURRENT
FOUR
ZONES
INTERNAL
PROX
READER
WIEGAND
INPUT
INTERNAL
DOOR
STRIKE
RELAY
7872
145mA + 1.6mA
per active zone
215mA + 2mA
per active zone
X X
7873
143mA + 1.6mA
per active zone
243mA + 2mA
per active zone
X X X X