Velleman PEM7D MINI INFRARED SECURITY SYSTEM, 7m easy to install, adjustable timer &amp; volume applications: entry detection, automatic alarm warning, present detection includes: 1 x retro-reflection IR photoelectric beam sensor, 1 x power supply 120VAC / 9V DC / 200mA, 1 x alarm speaker (timer &amp; volume adjustable) optional counter for PEM7D: PEM7D/C Assembled and Tested