GAI-Tronics 491-204 Mine Dial / Page Phone - Manual (Page 5)

Pub. 42004-195E
Model 491-204 Mine Dial/Page Telephone Page: 5 of 9
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Most of the electronic circuitry is located on a single plug-in PCBA, GAI-Tronics Model 69491-401,
inside the Model 491-204 Station. The circuitry associated with keypad and sidetone adjustment is
located on a small PCBA behind the keypad (Model 69491-002). All these circuits operate from a single
12 V NEDA 926 lantern battery also contained within the station. These internal components are shown
in Figure 3.
Figure 3. Internal Components
For each Mine Dial/Page Telephone station, a GAI-Tronics Model 69001-001 Interface PCBA must be
used. This assembly is a plug-in printed circuit board measuring approximately 7.5
× 4.5 inches (190.5 ×
114 mm) and must be mounted in a non-hazardous area within a Model 495-001 Mine Dial/Page
Telephone Interface Cabinet.