Installation Details:
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The Talk Back unit is installed in a standard 4x4 NRTL (UL/ETL) listed double gang switch box using four
6-32 x ½ black stainless-steel pan-head screws. A switch box is required as the 4 mounting screws line up
with holes that are only present on a switch box. The box needs to be at least 2-1/8” deep. The cabling must
exit the junction box on the lower right-hand corner of the bottom of the box. Sufficient cable service loop
must be present to allow the cables to be connected to the Talk Back unit and then fed out of the box as the
Talk Back unit is mounted. When an in-wall switch box is used, this extra cable can be easily fed into the
wall. If a surface installation is done there typically needs to be a pull box, j-box or other scheme employed
to allow for cable to be pulled in and out of the switch box during installation and removal. An example could
be a secondary 4x4 j-box below the Talk Back unit, connected to the switchbox with a suitable nipple.
The Talk Back units requires a 24v dc power feed from either a Lencore supplied HRP-150-24 power supply
or a Lencore PSM7A battery backed up 24v supply. With either supply a total of 15 units can
be fed off one supply (assuming 16AWG wire at 400 ft max from power supply to the last Talk Back unit).
The ground must be maintained on the Talk Back units, the same way Operating Platforms are wired.
In addition to power, the Talk Back sits on the system databus, and as such has a data in and data out
connection. Data cable: The maximum length of the Data cable is 3000 feet from the head-end to the LAST
device connected to the Data cable. A device can be an OP or talk-back module. The distance from talk-
back to talk-back is not relevant if the previous statement is met. To extend the data cable, adding a router
after the LAST device allows the Data cable to run another 3000 feet from the router.
See the flow diagram below (figure 1).
