5-220.127.116.11 Operator, using telephone handset, and crewmember, by pressing and releasing PUSH-TO-TALK button on
earphone and speaking into headset microphone, can communicate.
5-18.1.3 Two-way communications between crew personnel. Crewmembers can communicate with each other after
plugging telephone headsets into jack receptacles at headset stations.
5-19 Operating instructions
5-19.1 Operating controls and Indicators. Controls and indicators for the telephone system are shown in Figures 5-14
5-19.2 Prestart procedures. Following prestart procedures should be performed by operator before activating telephone
Perform before operation checks below:
Make sure telephone system installation is complete.
Check for corrosion or rust. Clean and touch up paint as necessary. See paragraph 5-7.2a.
Make sure knobs or buttons are not missing, broken, or loose and controls operate properly.
Check for loose plugs and jacks. Tighten if necessary.
Check for loose mountings, hardware, brackets, etc. Tighten as necessary.
Check for damage. Repair as necessary.
Make sure power switches are set to OFF position for all system operating equipment.
Make sure proper fuse ampere/voltage rating and type are installed in telephone
equipment. If a larger ampere-rated fuse is used, this equipment will be damaged.
Make sure telephone power control module has a 0.5 A fuse in the fuse holder on the side of the telephone
headset station selector (Figure 5-14).
Make sure circuit breakers are dosed (ON) in accordance with Table 5-6.
Table 5-6. Circuit Breakers
24 Vdc power
and strobe lights
Power panel 3
panel to provide
power to emergency
and strobe light