Panasonic VL-V901 Series Installation And Operating Instructions Manual page 76

5. Programming
Checking the polarity of wiring connections for gate call settings
For extension boxes with D suffixes or later for the serial number (page 92):
When configuring gate call settings when 2 or more control boxes are connected to an extension box, check the
polarity of wiring in the following way. Set DIP switch 8 to the "on" position, and set the lobby station DIP switch settings
for configuring gate call settings (page 75).
Connect the "+" side of the wire from the control box to L1 of the extension box.
Note:
R Make connections so that L1 on the control box and L1 on the extension box are connected.
1. After connecting to the control box side, measure the voltage of the 2 wires to be connected to the extension box
side using an electrical tester.
Extension box
NP
Up to 6
Lobby station
2. Connect extension box wires with the correct polarity as shown in the following.
If the electrical tester displays "approx. +5 V"
Connection to L2 of the extension box
−
＋
Connection to L1 of the extension box
76
＋ ＋ − −
Up to 4
Control box
DC IN
NP
POWER SUPPLY UNIT
−
＋
L1 - L1
L2 - L2
PC
If the electrical tester displays "approx. –5 V"
Connection to L1 of the extension box
−
＋
Connection to L2 of the extension box
Control box
PBX
RJ11
USB
DC IN TV Monitor
NP
POWER SUPPLY UNIT
NP: Non-polarised
＋
−
NP