Installation manual

D9124 Operation & Installation Manual
Page 39
© 1996 Radionics
74-06799-000-D 2/96
Telephone Connections
D928 Dual Phone Line Switcher
You must use two phone lines for a reporting fire system to meet UL and NFPA
standards.
Description
The D9124 uses the D928 to transmit reports over a second phone line. The D928 allows
the D9124 to monitor both the primary and secondary phone lines. For information about
connecting the D928 to the D9124, see Connecting Cables Between D9124 System
Components in the Installation section of this manual.
Operation
The D9124 always uses the primary phone line to initiate phone calls, unless it has been
detected as faulty.
Phone Line Monitor
The D9112LTB panel has a built-in phone line monitor that tests the phone line for
voltage and current. The panel monitors the primary and secondary phone lines as the
D928 regularly routes each line to the D9112LTB. The normal voltage on a telephone line
is approximately 48 VDC (24 VDC for some phone systems). The phone line monitor
senses trouble when the voltage on the line falls below 4.5 to 7.5 VDC, without a
corresponding current increase of 8 to 13mA.
If the monitor senses trouble, it starts a programmable phone line trouble timer. The timer
continues to run as long as the monitor senses trouble. It resets to zero when the panel
senses a normal line. If the timer reaches the delay time in the Phone SupervisionPhone Supervision
program item, it begins a phone line trouble response. Programming determines what the
response is. See Phone Parameters in the D9112B Program Entry Guide (74-06145-
000).
The panel stops monitoring the phone line during its phone line trouble response. If the
response includes sending a report, the panel does not resume monitoring until the report
is acknowledged or it goes into communication failure.
Bad line may test OK: The telephone line monitor uses voltage and current levels to
test the status of the phone line. In some instances a given telephone line may be out of
service without affecting the voltage on the line. The phone line monitor can not
recognize this trouble condition.
See the Phone section of the Panel Wide Parameter module of the D9112B Program
Entry Guide (74-06145-000) for phone supervision and reporting options. You must set
the Two Phone LinesTwo Phone Lines prompt to YES to use the D928.
Primary Phone Lines, Primary Phone Numbers
Don’t confuse primary phone lines with primary phone numbers: With the D928
Dual Phone Line Switcher installed, the D9124 uses two phone lines, primary and
secondary, to dial up to four phone numbers.
These four phone numbers are designated as primary, backup, or duplicate. See Phone
Routing in the Panel Wide Parameter module of the D9112B Program Entry Guide
(74-06145-000) for a description of these designations.