Basic Telephone Circuit Diagram - Electronic Circuit Schematics. Note that all these links are external and we cannot provide support on the circuits or offer any guarantees to their accuracy.. The circuit uses a 555 timer and a CD 4017 IC. The clock pulses for the CD 4017 IC are provided by the timer IC which is connected as an astable multivibrator. The pin number 14 of the CD 4017 IC is the clock input pin. When the clock pulses are fed to this pin, the 10 output pins become high one by. Description. This lead acid battery charger circuit is designed in response to a request from Mr.Devdas .C. His requirement was a circuit to charge two 12V/7AH lead acid batteries in series.Anyway he did not mentioned the no of cells per each 12V battery..