To determine user presence an additional sensor, external to the APS is included. This sensor senses for user engagement and is typically either:
- An infrared (IR) remote control sensor, or
- A multi-sensor (infrared and motion sensing)
The sensor works in conjunction with a countdown timer that resets each time user engagement is sensed. When no user engagement (absence) is sensed for a period of time, the countdown timer expires, and the TV is switched off automatically, thereby generating energy savings from both the TV and peripherals. The Tier 2 APS energy-saving principle is engagement and behavior based rather than relying simply on user behavior as with a Tier 1 APS.