This Power supply sources from 500 to 1,000 mA according the transformar and was found in a publication of the year 1958. The diodes can be now the 1N4004 and the transistor should be mounted on a heatsink.
Often, unauthorized people use the phone to make improper calls. A control for this is achieved with...
This circuit was obtained in an Electronque Loisirs magazine from France, in a July 1991 edition. It...
This circuit sensor is an NTC with a resistance of the order of 2k. The SCR can be from the TIC...