24 Vdc Central Power System; Figure 9 Typical Central Power System - Federal Signal SelecTone 300SCW-1 Manuel D'installation Et D'entretien

Installation and Maintenance Manual

24 Vdc Central Power System

See Figure 9. In the central power system, all of the remote amplifier power lines are connected in
parallel to one or more centrally located power sources that are 24 Vdc.
MODEL 300SCW-1
4 5
TB1
The advantages of a central power system are:
✓ The entire system may be independent of local line voltage.
✓ The entire system can be switched to an emergency standby power source in the event of a power
failure.
✓ The central power system has the added advantage that an auxiliary power supply, such as the
Federal Signal Model PS300 can be used to power the remote devices in the SelecTone system. If
the PS300 is used, it is not necessary to switch the power source if a power failure occurs.
The disadvantages of a central power system are:
✓ Heavy power lines are required from the power source to the remote devices in the system. The size
of the power lines is dependent upon the number of amplifiers and the total distance of the power
loop in order to minimize the voltage drop while a tone signal is being generated.
✓ Future expansion is limited by the current capacity of the power source and the power lines that
were initially installed.
✓ Central power installations must comply with local electrical codes. Most power circuits are Class I
circuits. Therefore, conduit will probably be required. Installation costs are higher than a local
power system.
16

Figure 9 Typical central power system

17 1 15 16
TB2
+ –
SIGNAL LINES
SHIELDED
TWISTED PAIR
+
24 Vdc
POWER OUTPUT
SUPPLY –
Model 300SCW-1 Wall-Mounted Command Unit
AC POWER IN
MODEL 300GC
120 Vac
MODEL
AM25CK
POWER
LINES
290A7539