GAI-Tronics 495-001 Mine Dial / Page Phone Interface Cabinet - Manual (Page 10)

Pub. 42004-198D
Model 495-001 Mine Dial/Page Phone Interface Cabinet Page: 10 of 22
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Monitor (One Pair)
This function is to supply approximately 20 mA dc to a relay in the interface cabinet that when
interrupted, switched the system into a merged operation. The nominal 48 V dc power available in most
switchboards can be used. Up to 1600 ohms series resistance can be tolerated. An adjustable resistor in
the interface cabinet, in series with the relay, can be set to limit the current if the 48 V dc is used directly.
An unused station line can also be used to supply this function. See “Adjustment of Switchboard Monitor
Circuit” on page 14 for details.
N OTE : The Monitor function must be connected for proper operation of the Mine Dial/Page Phone
system.
All-Call (Two Pair)
This function is taken from the paging capability built into, or provided optionally by, the PABX. One
pair from the PABX provides an “A” relay contact (normally open) and the other provides an audio
paging signal at normal telephone line level. The “A” contact will have to switch the positive leg of the
monitor voltage into an electronic relay circuit. Maximum current through the contact will be 30 mA dc.
See Figure 7.
The supplier of the PABX should install cable(s) for the station lines and the special lines to a termination
panel adjacent to the interface cabinet. Barrier terminal blocks are provided on the MDPP system for the
telephone line connection.
Wiring Mine Cable to the Interface Cabinet
The cable from the Mine Dial/Page Phone stations should be routed up the left side of the cabinet as seen
from the rear. The wires in this cable connect to terminal strips marked M
INE P HONE L INES . One wire
of each pair goes to a L1 terminal and the other goes to the corresponding L2 terminal immediately below
it. Proper polarity must be maintained in wiring this circuit. Where black and white coded wiring is
used, the white wire should be for L1 and black for L2. Refer to Figure 3.
The wiring within each PCBA Rack Assembly is such that the Interface PCBA Assembly in the number
one position completes a circuit from T
ELEPHONE L INES number one to M INE P HONE L INES number
one. The 491 Series Mine Dial/Page Phone No. 1 terminals will have the telephone number (extension
number) of the PABX line connected to T
ELEPHONE L INES No. 1 terminals on the same rack.
Any above ground 491 Series Mine Dial/Page Phone should be wired with the M INE P HONE L INES
terminal in the same fashion as those in the hazardous area. The precaution on transient voltage
suppressers also applies to the installation of these stations.
AC Power Connection - 120 V ac, 60 Hz, should be brought into the receptacle box at the rear near
the floor of the cabinet. All ac-operated circuits within the interface cabinet are pre-wired to this
receptacle box. The power line to the interface cabinet should have an independent 15-amp
(minimum) line. Be sure the AC
ON switch on the front panel of the Power Supply/Metering Panel
Assembly is in the down (off) position before applying ac power. See Figure 8.
CAUTION
Line-to-ground transient protection (such as nominal 450 V carbon/air-gap
or gas-tube lightning arrestors) must be installed on all PABX and 491 Series Mine Dial/Page Phone
lines exposed above ground.