ffd

Because of energy crisis Load shedding may be a common problem in several countries.. Sudden power fluctuations, surge and high voltage may spoil sophisticated household appliances like TV, VCR, VCP and music system. This circuit provides protection against these problems and automatically changes the power supply from Generator output to mains supply and also switches off the generator. Circuit descriptions This circuit is self explanatory. When lines supply voltage crosses the preset level, Zener diode ZD4 break down and thus transistor T2 conducts, T3 does not conduct, causing the relay to de-energise. Voltage surge at the time of power resumption is protected by the delay circuit around transistor T1. All the portable petrol and kerosene generators have a connection from CDI. To stop the engine of the generator-set, this connection is to be grounded momentarily (through the switch). This lead is to be connected with the ground through the N/C point of the relay. Auto Changeover ...

2 .Line Intercom Telephone Line Changeover .The circuit presented here can be used for connecting two telephones in parallel and also as a 2-line intercom. Usually a single telephone is connected to a telephone line. If another telephone is required at some distance, a parallel line is taken for connecting the other telephone. In this simple parallel line operation, the main problem is loss of privacy besides interference from the other phone. This problem is obviated in the circuit presented here. Under normal condition, two telephones (telephone 1 and 2) can be used as intercom while telephone 3 is connected to the lines from exchange. In changeover mode, exchange line is disconnected from telephone 3 and gets connected to telephone 2. . Circuit diagram: 2-Line Intercom-Cum-Telephone Line Changeover Circuit Diagram . For operation in intercom mode, one has to just lift the handset of phone 1 and then press switch S1. As a result, buzzer PZ2 sounds. Simultaneously, the side tone is h...