M50560 infrared transmitter circuit

Shown is an infrared transmitter circuit composed of M50560 integrated circuit . The ④ and @ pins of M50560 are connected to c3, C4
and quartz crystal oscillator X. They and the internal circuit form a clock oscillator, which can generate a 456 kHz pulse signal. After being divided by 12, it becomes 38 kHz with
a duty cycle of 1: 3 infrared carrier signal. The @ pin of M50560 is the output end of the modulation signal, and the transistor QI drives the infrared emission and the diode
DoI to work. K is the emission control key. As long as you press K, you can emit modulated infrared light.