Things You'll Need
Alarm system installation manual
Key for system panel (if applicable)
Regular and Phillips screwdrivers
You may want to disconnect your phone line from your security system for several reasons. When security systems become faulty, they can seize the phone line and make it impossible to place or receive calls. Additionally, if you have a cell backup unit installed, you no longer need a phone line connected to your system. You may want to disconnect it because you have discovered it is possible for someone to call your security system and hack into it, or if you have discontinued security monitoring.
Open your installation manual, locate the wiring diagram for your system (usually near the end of the book), and find the phone line terminals. This is two terminals on the alarm system circuit board. These are marked phone line, line in or something similar. They are usually toward the right end of the terminal block. Make a note of their terminal numbers or circle them in your manual.
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Find your alarm system control box. This is usually located inside the master bedroom closet or laundry room, but in nonstandard installations it could be anywhere within the house.
Open the metal box; you see a circuit board with wires going to it and a battery. On one edge of the circuit board you see a long row of screw terminals. Locate the two terminals for the phone line. That line should lead to a small box with a regular phone cord and connector attached to it; unplug the phone cord and skip to step 5. If you do not see that box, proceed to the next step.
Using a Phillips or regular screwdriver loosen one of the terminals, remove the wire, and wrap it in electrical tape. Disconnect the other wire, and wrap it in electrical tape. Retighten the terminals.
Coil the wire up, put it back inside the box, close the box, and secure the lid.
You may want to mark the phone line with some masking tape and a permanent marker in case you ever want to reinstall it. If you have an integrated system (keypad and alarm system in one unit--sometimes called a talking system), remove the unit from the wall. Unplug the phone cord and remount the system. If you do not have an installation manual, you can download it online. Just get the make and model number of your system and do a search. Make sure you download the "installation" manual; the owner’s manual does not contain the information you need.
Alarm systems are designed to be in a constant power-on status; your house power is permanently applied, so you are working on a live system. All of the voltages are low voltage/current and are not dangerous. However, you should be careful that you do not short out the terminals or other electronics or you may damage your system. You should not perform this task if your system is being monitored without calling the monitoring facility or you could trigger an alarm.