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All SelectFone system stations are connected in parallel. 24VDC stations draw 1.5Amp.
Max. current when page amplifier is driven by sine wave signal producing 12 watts in to an
8-ohm speaker. When planning 24VDC SelectFone system layout, careful consideration should
be given to the power cable losses due to the voltage drop caused by cable resistance. To
reduce the voltage drop in the long cable length it is recommended that several branches
from 24VDC-power source be used to power the system and no more then six (6) stations
should be connected to each power cable branch. An adequately rated fuse or a circuit breaker
at the 24VDC source should be used to protect each power cable branch. For a 14 AWG
power line this fuse or circuit breaker should be rated at 15Amp.The rating of the protection
device is based on size of the power cable. Consult the National Electrical Code (NFPA 70)
or Canadian Standards Association (CSA 22.1) for maximum allowable capacity of cable
size used.
Note that cable distance between stations as well as total cable length must be considered.
Table in this section will provide guideline for cable distance (length) and number of 24VDC
stations connected to it in parallel. This table is based on speech signal driving station speaker/
amplifier to produce full 12watt output into an 8-ohm speaker. It is also assumed that stations
are spaced at equal distance from one another along the cable length. A speech signal has
less energy content then continuous sine wave signal so the average current draw per station
is less then sine signal.
MAXIMUM CABLE DISTANCE PER POWERLINE BRANCH
14AWG CABLE
N
T
B
UMBER
OTAL
S
OF
S
TATION
1
4000ft
2
2800ft
3
2000ft
6
1200ft
9
800ft
The 24VDC power connections are made at the 3-position terminal block JP1 mounted on
the motherboard in the station enclosure. Connect the black positive (+) 14 AWG conductor
of incoming and out going power cable to the + terminal of JP1. Connect white, negative(-)
14 AWG conductor of incoming and out going power cable to the - terminal of JP1. Connect
the green/yellow the earth ground 14 AWG conductor to the GND terminal of the JP1 termi-
nal block.-
c.
Page Line and Party Line Connection.
To avoid electrical shock, do not connect wires when power is applied.
All the channel line and page line connections are made at the L1 and L2 terminal blocks
mounted on the motherboard. The incoming and outgoing cable of multi-channel systems
have six, differently colored, 18 AWG, twisted pair conductors. One conductor of each twisted
pair is of solid color and the other has a stripe of the same color.
1. As shown in Figure 1, the page line connections are made to the L1 and L2
terminal blocks, at the terminals marked L1 PAGE L2. Connect 18 AWG RED
conductor of twisted pair RED, WHITE/RED of the incoming and outgoing cable
to L1 and conductor WHITE/RED to L2 at location marked PAGE on the
motherboard.
12 AWG CABLE
T
ETWEEN
OTAL
TATIONS
4000ft
6400ft
1400ft
4480ft
660ft
3200ft
200ft
1920ft
90ft
1280ft
10 AWG CABLE
B
T
ETWEEN
OTAL
S
TATIONS
6400ft
10000ft
2240ft
7000ft
1060ft
5000ft
320ft
3000ft
142ft
2000ft
WARNING
-6-
8 AWG CABLE
B
T
ETWEEN
OTAL
S
TATIONS
10000ft
16000ft
3500ft
11200ft
1667ft
8000ft
500ft
4800ft
220ft
3200ft
B
ETWEEN
S
TATIONS
16000ft
5600ft
2667ft
800ft
356ft
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