Cordless Phone Backup


Posted on Feb 4, 2014

Normally the base of a cordless phone has an adaptor and the handset has Ni-Cd cells for its operation. The base unit becomes in-operative in case of power failure. Under such conditions, it is better to provide a backup using Ni-Cd cells externally. Here is a simple power supply back-up circuit which can be used with cordless phone SANYO CLT-420


Cordless Phone Backup
Click here to download the full size of the above Circuit.

or similar sets. The working is simple. When AC mains is present, Ni-Cd cel ls are charged through IC LM317L, which is wired as a current source. Also, diode D3 is reverse-biased, which keeps Ni-Cd cells isolated from positive rail. When AC mains goes off, the Ni-Cd cells provide supply to the cordless phone base unit through diode D3. A green LED is used to indicate the presence of AC mains. Each Ni-Cd cell costs around Rs 34, and the cost of the backup unit, including the box and cells, would not exceed Rs 300. Hence the circuit is well worth the investment.




Leave Comment

characters left:

New Circuits

.

 


Popular Circuits

Stereo Headphone Amplifier
Passive Audio Mixer
Direction and speed control for series-wound motors
Signal-combiner
Carrier-Current Receiver For Data Transmission
300w power amplifier circuit with 2n773
Peak Detector Circuit
1995 camaro: just swapped the engine/ trans with cradle wheel well
Two-way touch switch 4
Boombox circuit diagram
UPC1651 produced by small family video transmitter circuit diagram



Top