An infrared blaster is a device that emulates an infrared remote control to autonomously control a device that is normally controlled only by remote control key presses. The most common use of an IR blaster is to allow a recording device such as a DVR

Digital video recorder

A digital video recorder , sometimes referred to by the merchandising term personal video recorder , is a consumer electronics device or application software that records video in a digital format to a disk drive, USB flash drive, SD memory card or other local or networked mass storage device...

 or VCR to change the channel on an external tuner such as a cable box or satellite

Satellite

In the context of spaceflight, a satellite is an object which has been placed into orbit by human endeavour. Such objects are sometimes called artificial satellites to distinguish them from natural satellites such as the Moon....

receiver. This way, the recording device can automatically select the correct channel to record before starting the recording process. Another common use is to extend infrared signals in order to place remote controlled products behind closed doors.