You will need
- - mobile phone; - stabilized power supply; - voltmeter; - uninterruptible power supply; USB cable; soldering; - solder; - rosin; flux.
Remember that the standard charger for mobile phone designed to work in conjunction with a battery capable of short-term to provide large current. Feed directly from the intercom not. Otherwise, when you first turn on the transmitter the voltage drops to almost zero.
Purchase or fabricate a self-stabilized power supply with short circuit protection. It needs to develop a voltage of 3.7 V at a load current range to 2 A. Note that the voltage should not exceed the specified value during the fall of load or switching on and off of the apparatus.
Turning off mobile phones, disconnect the regular battery charger and remove the battery. Using a voltmeter, determine the battery has two contacts with the voltage from 3.2 to 3.7 V.
Observing polarity, connect voltage from the power supply to the respective contacts of the battery compartment of the phone. If you decide later to use a mobile device purely for the security system, unplug the power supply and solder joints of the contacts.
Turn on the power supply and try to start the mobile phone. If you managed - the device is not equipped with a data exchange module with built in battery chip. So, your intercom is suitable for use in the alarm system.
Avoiding disconnection if no voltage, connect to alarm the uninterruptible power supply. Install the unit in a place meeting the requirements of operation of the UPS.
Confirm the operation of installed you system. Connect the USB port of the mobile telephone with the security device, the common wire which is decoupled from the cable of the power supply apparatus.