I found an old Philips TV remote and of course took it apart. Inside there was just a PCB underneath the rubber button mass. Each button is actually a capacitive sensor. When the rubber bottom of each button comes into contact with the cap, it changes the amount of capacitance. This signal from the remote is transmitted via an infrared LED that the TV picks up and decodes. The picture below shows the LED on the top of the PCB. It’s labeled IED1.