of twisted pair VIOLET, WHITE/VIOLET to L1 and WHITE/VIOLET to L2 at location
PARTY 4 and for party line 5, connect conductor GRAY to L1 and WHITE/GRAY to
L2 terminals at PARTY 5 location.
d. Paging Speaker Connection
As output to the speaker from the speaker amplifier of the SelectFone station is less then 11
volts RMS, the speaker wires falls into CLASS II of the NEC code and, hence, conduit is not
required except for mechanical protection. To minimize power loss in the speaker cable, the
length of the speaker cable should be as short as possible. The table in this section shows the
wire size and corresponding maximum length of speaker cable allowed to maintain a cable
power loss under 20% (1db).
As shown in the Figure 1, the connection to the 8 ohm or 16 ohm paging speaker is made
at the terminal block marked JP2. Using 18 AWG twisted pair cable connect –VE terminal
of the speaker to the terminal marked C at the terminal block JP2 and connect +VE of the
speaker terminal to the terminal marked 8 for 8-ohm impedance speaker or to the terminal
marked 16 for 16-ohm impedance speaker.
It is recommended that when the Push-to-Page switch is pressed, the paging speaker connected
to that station is silenced (muted) to prevent acoustic feedback to the handset microphone.
This is why there is a jumper placed between terminals marked IN and OUT of the terminal
block marked JP2. This does not prevent the speaker connected to the muted station from
announcing the paging messages originated at other stations while channel line conversations
are being carried out at the muted station.
Removing the jumper between IN and OUT terminals will disable the mute feature.
Wire Size
8 OHM output
16 OHM Output
#18 AWG
75 FEET(25 M)
150 FEET (50 M)
#16 AWG
120 FEET (35 M)
240 FEET (75 M)
#14 AWG
200 FEET (60 M)
400 FEET (120 M)
e. Line Balance Assembly Connection
One line balance assembly Model SF-1000LB must be installed with each SelectFone sys-
tem. It should be located at the electrical center of the system. The line balance assembly
properly loads the page line and all channel line circuits. Locate the line balance assembly
unit within 12 inches of the SelectFone station located at the electrical center of the intercom
system. See Fig. 6.
1. Remove the cover by loosening the four screws.
2. Place the rear of the housing against the mounting surface. Using the four mounting holes
located in each corner of the enclosure as a template, scribe mounting hole locations on
the mounting surface.
EQUIPMENT DAMAGE HAZARD
To avoid damage when drilling, ensure that both sides of the mounting surface are clear of
any parts or wires. Drill the holes only through the desired surface.
3 The line balance assembly is supplied without conduit or cable entry holes. Drill or
punch the necessary conduit or cable openings in the enclosure before mounting it to the
surface. Remove all the metal shavings and debris from the enclosure.
4. Drill four holes at the scribed mounting hole locations. Remove all burs and sharp edges.
Secure the housing to the surface with the user-supplied hardware.
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