4
HOW THE LINKS1000 WORKS
Cellular Communications
All cellular telephones, including the LINKS1000, must ‘register’ with the cellular network. ‘Registration’ is
simply a handshake, sending ESN and Telephone number, between the cellular switching station and the
cellular telephone. This is done upon power up of the LINKS1000 and randomly once a day. If the phone does
not register the network will not complete a call. Tower signal strength, also called RSSI (receive signal
strength indication) is updated approximately every 4-5 seconds. RSSI is indicated as a go/no go visible via
the RSSI LEDs (L3, L4, L5, L6).
Sending an alarm
Before dialing the central station, all DSC alarm controls perform a telephone ‘line-test’. This is done via the
control unit using a series of off-hook and on-hook transitions to verify dial-tone. This takes 30 seconds.
The control panel ‘line-test’ feature will only determine a telephone line is inoperative when it is attempting to
send an alarm. With a LINKS1000 connected, the control panel will send the central station telephone number,
in a digital format, from the PGM output of the control panel to the PGMIn input of the LINKS1000. The
LINKS1000 then accesses the cellular telephone network and begins dialing. Once a suitable channel is
established the LINKS1000 switches an onboard relay and establishes a connection between the TIP and
RING terminals on the control panel and the T1 and R1 terminals on the LINKS1000.
With cellular communications now open to the central station receiver, the panel will detect ‘handshake’. The
alarm is sent. If the message is received, ‘kiss-off’ is sent, just as if it were communicating over a standard
telephone line. Once the panel has completed the transmission, the control panel ‘hangs up’. The LINKS1000
then detects the loss of current across T1 and R1 and sends the END key to the cellular network.
Telephone Line Monitor
The Telephone Line Monitor is a separate feature integral to DSC or Sur-gard control panels PC1575, PC1580
and higher. The TLM looks for a 30 second loss of telco line voltage. With a LINKS1000 connected and TLM
signaling enabled, a service outage would trigger the panel to begin dialing though the LINKS1000. Dialing
will begin after the TLM time-out and ‘line-test’ are complete. This should take 1 minute.
Trouble supervision
Trouble supervision of the LINKS1000 is provided in one of two ways:
When Jumper J1 is ON (shorted), a general system trouble indication is used at the LINKS1000 SYS TBL
terminal. All trouble indications will trigger this output to the control panel.
When Jumper J1 is OFF (removed), there are three separate trouble outputs: AC TBL, Bat TBL, and the
LINKS1000 SYS TBL. The AC TBL terminal and Bat TBL terminals are each used to indicate their respective
troubles. The LINKS1000 SYS TBL will activate for all other troubles. These outputs are connected from the
LINKS1000 terminals to separate zones on the control panel. The zone(s) should be programmed as 24-hour
silent except on the PC1575, PC1580, PC4010, PC4020, PC4020KT, PC5010, PC5015, PC1555, PC1565,
PC5008, PC580 and PC585 where a zone (or zones) is designated for LINKS1000 supervisory. Under normal
conditions, the TBL outputs of the LINKS1000 are “open”. When one or more of the six monitored trouble
conditions are present, and the corresponding time-out has expired, the respective output will be pulled to
ground. The connection from the LINKS1000 TBL output to the control panel zone, forces the zone to ground.
The panel now has an alarm it must send and the dialing sequence begins. Typically, trouble signals are sent
via the telco line. If the telephone line is not operational, the panel will send the signal via the LINKS1000 and
the cellular network.
This configuration is required on UL Listed systems.
