Section II. Description of operation
4-9 General. The telephone system has 11 major components telephone station selector box containing power amplifier
and power control module, speaker, headset, buzzer, strobe light, crew headset station, system operator handset station,
25-foot headset extension cord, and headset stowage box. These components of the telephone system are used for
paging between the dayroom system operator and crew personnel and for two-way communications between crew
telephone stations. Various modes of communicating with this system are discussed in paragraphs 4-9.1 thru 4-9.3.
4-9.1 Paging from system operator to crew personnel. When system operator in dayroom selects crew telephone
station to be paged on telephone station selector panel and presses BUZZER switch on selector, station buzzer will
sound and/or station strobe light will light.
4-9.1.1 Crewmembers upon hearing buzzer or seeing white strobe light, are alerted to connect their headset into headset
station jack receptacle. To speak into headset microphone to let the system operator know that he is online, the
crewmember must press the PUSH-TO-TALK switch on the earphone. To listen to the system operator, the crewmember
must release the PUSH-TO-TALK switch.
4-9.1.2 As soon as crewmember is online, system operator stops buzzer/strobe by pressing BUZZER switch to OFF
position. To speak, operator must remove telephone handset from cradle and speak into the handset microphone.
4-9.2 Paging from crew personnel to system operator. After crewmember plugs telephone headset into headset
station jack receptacle, depresses PUSH-TO-TALK switch on earphone, and speaks into microphone, his voice will be
heard from dayroom speaker.
4-9.2.1 Upon hearing speaker page, system operator responds by selecting station to be communicated with on
telephone station selector box, removes telephone handset from cradle, and speaks into handset microphone
4-9.2.2 Operator, using telephone handset, and crewmember, by pressing and releasing PUSH-TO-TALK button on
earphone and speaking into headset microphone, can communicate.
4-9.3 Two-way communications between crew personnel . After crewmembers plug telephone headsets into jack
receptacles at headset stations, they can communicate with each other.
Section III. Operating instructions
4-10 Operating controls and Indicators. Controls and indicators for the telephone system are shown in Figures 4-2
4-11 Prestart procedures. Following prestart procedures should be performed by operator before activating telephone
a. Make sure power switches are set to OFF position for all system operating equipment.
Make sure the 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.
b. 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 4-2).
c. Make sure circuit breakers are closed (ON) in accordance with Table 4-2.