The ports used in this ultrasonic remote-control transmitter are TTL, requiring a 5 V supply. The transducer is a piezoelectric type, not very common today.
Circuits similar to this appear elsewhere in this section. The transistors can be BC549 (low...
September 2017 - Vishay Siliconix SQ MOSFETs for automotive use are in stock for immediate...
In this circuit we show how to modulate the pulses produced by a 555 in frequency. The circuit can be...