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In operation, when the relay is deactivated, the 100uF capacitor will charge to 6 volts. When the button is pressed, the capacitor will apply 6 volts to the MOSFET gate turning it on. The capacitor voltage (and gate voltage) will fall from 6 to 3 volts in about 200 mS which should be enough time for the relay contacts to move. For very slow relays, a larger capacitor may be needed.... [read more]

High Quality unit. No need for a preamplifier.... [read more]

A very high quality intercom, which may also be used for room monitoring.... [read more]

This circuit provides a visual 9 second delay using 10 LEDs before closing a 12 volt relay. When the reset switch is closed, the 4017 decade counter will be reset to the 0 count which illuminates the LED driven from pin 3. The 555 timer output at pin 3 will be high and the voltage at pins 6 and 2 of the timer will be a little less than the lower trigger point, or about 3 volts.... [read more]

Unlike many units, this battery charger continuously charges at maximum current, tapering off only near full battery voltage. In this unit, the full load current of the supply transformer/rectifier section was 4.4A. It tapers off to 4A at 13.5V, 3A at 14.0V, 2A at 14.5V and 0A at 15.0V.... [read more]

The particular circuit combines enough operations, as: [ 1 ] Smooth departure of benefit of AC line of network, with delay 1sec, to the transformers of power supply of amplifier, via the RL1 and the resistance Rx. (see block diagram). [ 2 ] Delay of connection of expenses of final amplifiers, in headphone, in order that noises emanating from the charge - uncharged of capacitors of power supply, they do not pass in them. Simultaneously becomes control of exit of amplifiers for existence of continuous voltage [DC]. If all go well it connects, the amplifiers in loudspeaker.... [read more]