What Is an IR Pass-Through?
A 2010 global survey by Logitech found that a majority of households have four or more remote controls for their home-entertainment centers. To control a device with a remote, the device must be visible so it can receive the remote-control signal. If you want to hide a device behind a cabinet door, you can use an IR pass-through cable with your television to replicate remote-control signals to the hidden device. An IR repeater enables you to replicate the signal from a remote control to more than one hidden device.
Your Remote Is a Flashlight
Imagine that you used a flashlight instead of a remote control to control your DVD player. To play a DVD, you would flash a signal by turning the light on and off a certain number of times. If you pointed your flashlight at the ceiling, however, your DVD player probably wouldn't respond, because the light from the flashlight would never reach it. As it turns out, your remote control is a flashlight, but the light pulses it sends to a device are in the infrared light spectrum, which can't be seen by the human eye.
Light Can't Penetrate Cabinet Doors
Just as the light from a flashlight can't be seen on the other side of a wall, door or cabinet, the light from an infrared remote control can't penetrate these barriers either. If you build or buy an entertainment system cabinet that hides your television behind cabinet doors, you must open the cabinet doors to reveal the infrared receiver on the TV to use the remote control. That's typically not an issue, since you can't see the television screen if you don't open the doors. However, to control a DVD player or other device with a remote control, you must also expose their infrared receivers, which might not be preferable.
Use an IR Pass-Through Cable to Control a Hidden Device
In addition to an infrared receiver for remote-control input, many televisions have a remote control output jack for an IR pass-through cable. One end of the cable has a connector that plugs into the output jack. The other end of the cable has an IR transmitter like the one in your remote control, which you place on top of the IR receiver on a device that's behind a barrier such as a cabinet door. When the TV receives an IR signal, it sends the same signal through the pass-through cable, which flashes the IR signal directly into the other component's receiver.
Use an IR Repeater to Control More Than One Hidden Device
To control more than one hidden device, you can also purchase an infrared repeater system. Repeaters come with their own IR receiver for input and have more than one output jack. Place the IR receiver in a location where it can receive the signal from a remote control, such as a universal remote, and connect the hidden devices to the repeater. The repeater will send the signal it receives to each connected device.