Cordless phone backup circuit


Posted on Oct 31, 2012

Normally the base of a cordless phone has an adaptor and the handset has Ni-Cd cells for its operation. The base unit becomes inoperative in case of power failure. In such conditions, it is better to provide a backup using Ni-Cd cells externally. Here is a simple circuit which can be used with cordless phone SANYO CLT-420 or similar sets. The working is simple. When AC mains is present, Ni-Cd cells are charged through IC LM317L, which is wired as a current source.


Cordless phone backup circuit
Click here to download the full size of the above Circuit.

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

RF Isolator
200 watt Audio amplifier with STK4050
Quad op amp generates 4 waveforms
Siren system circuit
fm if mw radio receiver circuit using la1260 ic
Phantom Powered Microphones
GPS reference clock NTP server with Gentoo
Another Arduino project for newbies
Automatic temperature control circuit



Top