The schmitt triggered connection of transistors can be explained briefly: If the voltage applied to the relays does not reach to zero or maximum value, the contacts will vibrate as the magnetization of the relay coil is insufficient. This situation is not desired in the relay circuit. Because the vibration causes sparking (sparking), causing rapid deterioration of the contacts of the relay. In order to minimize the vibration in the relay contacts, the transistors are connected with a schmitt.
The Schmitt triggered turn-off time circuit operates as follows: T1 is in the cut because C is not empty when energy is supplied to the given circuit. Therefore, the value of the voltage at the collector end of the T1 (point A) is at the maximum level relative to the ground. Therefore, T2 immediately transmits the relay by transmitting and the receiver operates. C and C starting to charge through the pot, fill out T1 after a while. As the voltage decreases in the collector of T1 (point A), the voltage decreases at the resistor R3 (point B) connected to the emitter. This causes the T2 transistor to be cut rapidly ( due to two electrical effects ).
1. The voltage at the collector of T1 drops and leads to T2 cutting.
2. The voltage generated by the resistance of R5 in which the emitters of T1 and T2 are connected has a reducing effect on T2. ( Negative feedback )
If the B button is pressed, the T1 will go straight to the cut. This causes T1 to increase the collector (point A) voltage, thus transmitting T2. As a result, the schmitt triggering method allows the relay to go into the transmission or cutting very quickly.