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Section 5: Operating Principles
Section 5: Operating Principles
5.1 Simulated Landline Mode
The simulated landline provides the alarm control panel (with dialer interface) with a backup line in the event
of PSTN line trouble.
Note:
The LE4020/LE4020CF must be programmed as a backup communicator for Simulated Landline mode
to operate.
If the voltage on the landline terminals (TIP/RNG) drops below 2.8V for a period of between 10 and 45
seconds - depending on the alarm control panel connected to the T1/R1 terminals- the LE4020/LE4020CF
switches the connected telephone device to the cellular network. After waiting between 30 and 40 seconds, it
checks the landline for one of the following:
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If the landline has been restored, the LE4020/LE4020CF switches the connected device back to the
landline, OR
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If the landline is still down, the LE4020/LE4020CF continues the simulation until the landline is
restored. The LE4020/LE4020CF will not switch during ongoing calls.
Note:
When the landline is down, the LE4020/LE4020CF provides a dial tone to any device connected to T1
and R1, including any telephones on the premises. The phones on the premises are not, however, able to dial
out over the LE4020/LE4020CF.
5.2 Panel Transmission Monitoring (PTM)
The LE4020/LE4020CF can also monitor the panel’s attempt to communicate with the central station. If it
determines that the panel is having difficulty, it switches the line to the cellular network. This feature is only
active when the LE4020/LE4020CF is configured as a backup communicator. This feature is in addition to the
regular line voltage detection.
The LE4020/LE4020CF monitors the phone line for four consecutive failed attempts within a 12-minute win-
dow. A failed attempt is assumed to have occurred when a line seizure takes place during dialing (either the
alarm panel or the customer telephone), but no 1400Hz tone (Contact ID kiss-off) or 2025Hz tone (SIA kiss-
off) is sent from the receiver.
Once the conditions for a failed attempt are met, the LE4020/LE4020CF connects the panel to the cellular net-
work to communicate the events. When the LE4020/LE4020CF switches the line it stays in this mode until
the panel hangs up. On the next event the LE4020/LE4020CF restarts the error detection sequence before
switching.
The LE4020/LE4020CF performs this sequence on any phone number that is detected on the line. Specific
central station phone numbers can be programmed into the LE4020/LE4020CF if desired. Up to four, 20-digit
numbers can be added to your profile at Connect 24. If programmed, the LE4020/LE4020CF only looks for a
Contact ID or SIA kiss-off after these numbers are dialed. A Telephone Line Monitoring trouble (PGM output
activation and/or reporting code if applicable) is also activated and/or transmitted when the PTM is activated.
A restoral is sent at the end of the call.
5.3 Cellular Communications Sequence
When an alarm is triggered:
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The control panel goes off-hook.
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The LE4020/LE4020CF asserts a dial tone.
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The control panel dials the number of the central station. Ensure that the alarm panel inserts a minimum
one second pause, or has Dial Tone Search enabled before dialing the number.
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The LE4020/LE4020CF detects the DTMF dialing and stops dial tone.
Note:
The LE4020/LE4020CF is unable to decode pulse dialing.
