Telephone Line Manager
STC 105C
Verifies Telephone Line Integrity
D.P.D.T. Relay Output
Dual Line Switching Capability
N.O. or N.C. Alarm Panel Output
Voltage and Current Monitoring
Selectable Delay
Microprocessor Controlled
Description of device and operation
The STC Model 105 Telephone Line Manager is a powered ancillary device for monitoring telephone line voltage. The device is completely isolated electrically from
the monitored line by optical coupling. It repetitively interrogates the telephone voltage to determine if the voltage
exceeds the preset minimum threshold. When the voltage
falls below this minimum for more than the selected delay
interval, the D.P.D.T. relay switches, the alarm output contacts change state, and the alarm LED lights. When any
“in house” device (such as a fax, alarm panel, or computer
modem) is using the telephone line, the STC 105 current
monitoring circuit decreases the threshold for an alarm
condition to virtually eliminate false alarms created by
normal telephone equipment operation. An alarm condition will auto-restore 5 seconds after the line voltage returns to normal. The relay output can be used to directly
select a second line or backup communications link, operate audible devices, trip zones on the alarm panel, or enable an “audible on line fault”. The alarm output is an
opto-coupled N.O. or N.C. dry contact (selectable) designed to directly interface with the alarm panel zones. The
12 V.D.C. power needed to operate the Line Manager is
derived from the auxiliary power output normally available
from the control. The compression terminals are convenient to use and the double-sided foam tape mounting makes
installation quick and easy. An earth ground terminal is
supplied to support the lightning and spike protection circuits.
Min. Telephone Line Voltage:
2.8 no load, .5 off hook (At house phone terminals)
Supply Voltage:
10-15 VDC, reverse polarity protected
Supply Current:
30 ma. average quiescent, 90 ma. in alarm
Input Impedance:
10 Megohm minimum
Line Isolation:
Opto-isolator, 5000 V. peak standoff, 50 Megohm,
telephone line to power supply
Alarm Output:
Opto-isolator dry contact, selectable N.C.
or N.O., auto-restoring, 20 milliamp continuous load
Switching Output:
D.P.D.T. relay, dry contacts, 2 amp. auto-restoring
Time Delay:
Selectable 10, 30, 120 seconds, line fail to alarm
condition (+/- 1% microprocessor controlled)
Time to Restore:
5 seconds
Light Emitting Diodes, Alarm and Line Check
1.75” wide X 4.00” long X 0.80” high (including
mounting pads and terminal blocks)
2 oz. (Shipping weight: 6 oz.)
Compression Type, Euro style barrier block
Double sided foam tape (supplied)
Two years parts and labor. (See separate warranty
statement for complete details.)
Ordering Information
STC 105C Telephone Line Manager
Installation Instructions for STC 105C
Telephone Line Manager
1. Mount the 105 PC board using the attached foam tape if the terminal blocks can be reached for wiring after mounting the
Manager. If the PC board cannot be wired after being installed, skip the mounting and proceed with the wiring in step 2. and
mount the unit after completing the wiring.
A. Monitor the telephone line with an alarm output to the panel on telephone line failure. (see Figure 1)
B. Monitor the telephone line, provide an alarm output to the panel, and enable an audible device or sounder during the
failure. (see Figure 1)
C. Monitor the primary telephone line, provide an alarm output and switch to the alternate phone line or cellular backup
for the duration of the primary line failure. (see Figure 2)
3. Connect the telephone line(s) and other devices as shown in the appropriate figure below.
4. Connect 12 VDC from the panel “AUX PWR” or from a regulated 12 VDC source as shown in figure 1 or 2 below.
5. Test by disconnecting the “TELCO IN” wires. An alarm condition will occur after a delay of the selected time interval.
6. Reconnect the telephone line and verify that the alarm condition clears and correct signals were received by the Central Station.
For Situation A or B, Wire and set jumpers as instructed in Figure 1 below.
Figure 1.
Com To alarm panel
12 VDC
Telco Line
in (RJ31)
Alarm panel
“Telco In”
Select N.C. or N.O. alarm
output with jumper
output from
10 sec.
Select time delay with jumper. 30 sec.
Set as shown on board
120 sec.
12 VDC
Alarm panel
“Telco In”
Telco Line
in (RJ31)
Figure 2.
To 2nd Telco Line or
Cellular Backup
For Situation C, wire and set jumpers as instructed in Figure 2. above
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