In an emergency situation in your living room, how do you warn your secretary in the front room? A good feature for those who wish to avoid dangerous situations is a secret switch, triggered by a magnet placed on any piece of decoration on your desk.
The stethoscope is a sensitive device that allows you to hear very weak sounds, being therefore a useful device for the detective. With it we can detect the noise of mechanisms of a clock bomb (if it is of the mechanical type) or even find hiding places and even listen through walls.
A powerful siren can be used for various purposes. It can be used in alarm systems to chase away intruders or even to warn that the enemy has "fallen" into a trap.
The following circuit serves to detect the passage of a person by a place, activating a warning at a distance or a recorder of time mode.
An interesting possibility of becoming incognito in a telephone call is to send a signal that can not be understood by someone listening to the recording. One type of interesting equipment for this purpose is the "scrambler".
For direct remote listening we can use a small amplifier that powers a headset. A battery-powered amplifier that can be loaded into a case along with the microphone is an interesting device for the detective.
This circuit can be used as a polarity indicator shield the direction of current circulation for...
This circuit for the automatic activation of a small lamp (or high brightness LED) was found in...
This optical pass-through shield can be used in various applications, such as object sensing or...
This circuit is characterized by the configuration that accelerates the switching, being ideal for the...
The power source shown for powering for small TTL circuits was found on a Radio Electronics...
IGBTs are widely used in frequency inverters, power controllers, switched sources and DC/DC...
This oscillator can run in frequencies up 10 MHz depending on the Power supply voltage. The 1 µF...
This one-digit counter is part f the samples bench of the MultiSIM in one of its versions. The...