This article is to introduce the infrared remote control extension circuit principle diagram. Do you have any idea on the circuit and opinions, welcome to contact us. At the same time also hope that this article is helpful to you. Do you think you could understand the circuit there are several important components LM7805 , BC109C and so on. The IR1 module (the IC3) is 5 v dc. This is the 7805 voltage regulator, IC1. Under the condition of static (no infrared signal), high voltage output pin, about 5 v dc. This needs to be inverted and buffer driver emitter LED infrared photo, LED2. Buffer is written by a door (pins 2 & 3) a hex inverter CMOS 4049, IC2. Modules can be driven directly IR1 TTL logic, but a pull-up resistor, R4 need interface of CMOS integrated circuit. This resistor to ensure that the signal from a remote control will alternate 0 and 5 volts. As TTL logic level is slightly different from CMOS, 3.3 k resistor R4 is connected to the 5 v power supply line to ensure high logic signals will be 5 volts and not 3.3 v TTL level. The resistance does not affect the performance of the infrared module, but and ensure that the correct module will drive CMOS buffer is not stable. The output of the direct drive transistor Q1 4049 pin 2, 10 k resistor R1 limit base current. Is a red leds LED1, it will display when a signal is received from a remote control. Note that in this circuit, the carrier still exist, but in levels drop, and decoding the infrared signal. And 4049 years of CMOS transistors will be two carrier and signal amplification BC109C drive LED2 in peak current is about 120 ma when a signal is received. If you want to measure this with a digital meter, it will read less, about 30 ma for the meter will measure the average dc values, rather than the peak current. Any equipment design work 36 to 40 KHZ should work, any control and carrier frequency will decrease the limits, but should work. There is a special case, some satellite receivers have infrared control, using a higher carrier modulation of about 115 KHZ.