The basis of a capacitive relay — a low-power generator of high frequency such as local oscillator of a radio receiver. To the circuit L1C4 (see diagram) of the connected metal plate sensor. Approached to him the palm of the hand represents the second plate of the capacitor CD. The capacity of such a condenser is the greater, the more area it covers and the smaller the distance between them.CONTACTLESS CAPACITIVE RELAY
The basis of a capacitive relay — a low-power generator of high frequency such as local oscillator of a radio receiver. To the circuit L1C4 (see diagram) of the connected metal plate sensor. Approached to him the palm of the hand represents the second plate of the capacitor CD. The capacity of such a condenser is the greater, the more area it covers and the smaller the distance between them.
Perhaps the most difficult stage in the process of creating radiokonstruktor — setting. But if you have even the simplest instrumentation, to establish any electronic device will be much easier. At least, for this job you need avometr, or simply tester. For example, very popular among ham radio uses a simple inexpensive device C-20. But the problem is, he is not entirely comfortable, and this tester is limited. So for those of you who already have such avometr, we propose to improve it by extending the limits of measurement and adding the generator probe with the test transistors.
To the line “Start” suitable for a student with basketball ball in hands, and comes on the panel associated with the starting button of the examiner, the Machine still does not work: it can be switched on only after the button is released.
Before describing the operation of the device as a whole will focus on one of its constituent elements — the Converter of the spectrum of the electrical signal, or “FUZZ”device. To To obtain this effect, it is necessary to enrich the original signal a large number of odd harmonics. There are several ways, and thus the schemes to achieve them. We will stop at the spectrum Converter, which is a ULF with parapremium.
First steps in radio, many often begin with independent fabrication of a transistor radio. Along the way, introduces the electronic components, acquired the skills in installation and work with measuring devices. And achieve rapid practical results is to the same positive stimulus for further study of fundamentals of electronics, gives confidence in their abilities and capabilities.
Electronic devices based on microprocessors and integrated circuits are less sensitive to the parameters of the supply voltage. To ensure the safe operation of these devices use voltage regulators with protection. In many power supplies is reduced to cut power to the circuit if a short circuit in it or a sudden increase in load current. Such, for example, the popular voltage stabilizers КР142ЕН5. 
As you know, speaker of the personal computer (PC) it is necessary to include separately. If they are installed at some distance from the operator, this situation is hardly comfortable, especially if the user wishes to view on a DVD movie recorder or any other video, accompanied by sound effects.
Two LEDs with different color (e.g., red and green), you can build a simple indicator for voltages from 4.5 to 220 V. It is also able to determine the polarity of the source in the range 8-220 V. When measuring AC voltage, both diode glow, but if it is constant — lights one of them depending on the wiring polarity indicator. The scheme proposed by the Czechoslovak journal “Amaterske Radio”.
The well-known school electroscope, which demonstrate the phenomena of electrostatics, determines only the presence of electrostatic charge. What is it, positive or negative, we can only guess. This shortage is deprived of the device designed for young hams syut Nadvirna town, Ivano-Frankivsk region. It not only determines the sign of the charge, but also its approximate size.
Our magazine has already told about this exciting game, made on the electromagnetic relay (see “M-K” №1, 1976). And today hams instead of contact devices are widely used in their structures with modern elements as transistors, thyristors, LEDs, integrated circuits. New versions of the game “Who is faster?” with the use of such devices and readers.