Relay with self-interrupter
The next example takes advantage of the delay between control pulse and actual switching, by a trick. If the button is pressed, a current ows into the relay, which is then activated. But this interrupts the current ow, because of the switch is connected in series with the power and the relay deactivates again. This again will activate it and so on. The process is repeated until the push button is released and interrupts the power supply. But no worry: The relay is internally protected against damage by too rapid back and forward switching and overload. The reaction time is in range of milliseconds (e.g. 10ms). Compared to the so called gain bandwidth of a modern transistor with around 1 GHz = 1000,000,000 Hz a relay is around ten billion times slower with its 100 Hz switching frequency in this example.