Figure 3-1. Model 300MB Rear View.
enable and signal in terminals. The SIG COM termi-
nals (TB1-16) of both uinits also need to be connected
together as shown in figure 3-2.
3-7. SIGNAL LINES.
The signal lines transfer the messages from a
CommCenter to the remote SelecTone devices. In
order to reduce the possibility of cross talk, hum, and
static noise pick-up, the signal lines must be twisted
pair audio cable. In the majority of systems, use
AWG 18 twisted pair audio cables. Shielded, twisted
pair cable is recommended when the Class II signal
circuit is in the vicinity of welding equipment, carbon
arc equipment, or similar electrical devices. Never
use a cable having wire smaller than AWG 22.
Federal Signal Corporation does not recom-
mend that new or existing telephone lines be
used as signal lines in a SelecTone system for
the following reasons:
1.
Interference from other services or
systems, or interference from the
system to other services.
2.
Cross talk, interference, or hum
induced by other telephone lines.
3.
Extended downtime because of the
second party involvement required to
service the lines.
4.
The additional cost of installation,
interfacing devices and monthly
charges as opposed to a one-time cost
of performing the installation.
3-8. MODEL 300MB SIGNAL CONNECTIONS.
Mixing signal lines with power lines could
cause electrical interference, which could
impede or render the system inoperable. Do
not install signal lines in the same conduit
with power lines.
To connect the signal lines of the SelecTone sys-
tem to the 300MB, connect a color coded twisted pair
of audio cables having conductors no smaller than 18
AWG to SIG HI (TB1-15) and SIG COM (TB1-16) ter-
minals on TB1 (see figure 3-1). Every remote Selec-
Tone signaling device in the system will be connected
in parallel to these lines. When connecting the remote
devices in parallel to the signal lines, observe the
correct polarity and install wire nuts over the con-
nections. The yellow wires on the 300CK should be
connected to the SIG HI while the blue wires should
be connected to SIG COM.
The 25Vrms speaker output is available at
TB1-13 and TB1-14 for direct connection to ceiling
speakers (see figure 3-1). Remove the labeled jumper
from terminals TB1-13 and TB1-14 of terminal block
TB1, before using these positions. Signal line losses
3-3
NOT USED
NOT USED
+ 24VDC
- 24VDC
POWER DOWN
NO
NC
COM
ENABLE
SIGNAL
MIC OUT
SIG COM
SIG HI
SIG
SIG
SIGNAL
ENABLE
COM
NC
NO
COM
MESSAGE
1
MESSAGE
2
MESSAGE
3
MESSAGE
4
MESSAGE
5
MESSAGE
6
290A2923
PTT
RELAY
CASCADE
IN
CASCADE
OUT
POWE
R
MONITOR
RELAY
25 VRM
S
LINE
GND
120/240 VAC
CLASS II FIELD WIRING
COMPARTMENT
CLASS I FIELD WIRING
COMPARTMENT
KNOCK-OUTS IN REAR OF HOUSING
MODEL 300MB REAR VIEW
(BACK OF HOUSING IS REMOVED FOR CLARITY)
OUTPUT LEVEL
TB2
TB1
10 9 8 7 6 5 4 3 2 1
17 16 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1
