|Radio and Electronics (DED Philippinen, 66 p.)|
In older books you find as an explanation for the term Electronics: Electronics are electric devices in which in some components the electrons are flowing in gases. Components which let the electrons flow in gases, are VALVES.
But even if you have only a very vage idea of the components found nowadays in radios, you know very well, that there are rarely used valves.
Additional you might know too, that radios are only one example of an electronic device.
In all those electronic devices nowadays there are used transistors instead of valves. Transistors are so-called SEMICONDUCTING components. But if all electric devices including semiconducting components would be called electronic devices, the term would be no more helpful.
Because almost each electric device includes this type of components now. During the last decades more and more electric circuits have been invented which had mainly the purpose to control another electric circuit.
To give an example: In a so-called voltage-stabilizer you will find a circuit which would measure the voltage at the input of the stabilizer, and the circuit of the equipment which needs the stabilized voltage. The second circuit will be controlled by the first one, in order to keep the voltage at the sensitive equipment stabile. Controlling in this connection can most simply be: to switch off and on, the lamp, or to dim it. This controlling was done at first by relays or by motoroperated rheostats. The relays and the motor driven rheostats are so-called ELECTROMECHANIC components. In such a component there are always moving parts, and this fact has two main disadvantages:
1. the speed of reaction of these components is rather low (a relays for example is only able to switch off and on 100 times/second)
2. the moving parts are worn out very fast, therefore the service life of those components is rather limited. (relays can be operated only about 1 million times). So it was very important to search for means of controls which do not have those disadvantages.
When the development of radios started it was depending on the development of components like valves, transistors and thyristors. With those new components it was possible now to control circuits:
1. directly without a mechanic interface, and
2. with much higher speed (several million times per second).
So let us agree on the following definition for this script here: CIRCUITS WITHOUT MECHANICAL SWITCHES WHICH ARE DESIGNED TO CONTROL OTHER CIRCUIT SWITH A VERY HIGH SPEED OF REACTION ARE CALLED ELECTRONIC CIRCUITS