Promaster SystemPRO Wireless Remote, SonyThe PROMASTER SystemPRO Wireless Remote Shutter Release uses Radio Frequency to trigger the shutter release of the camera. By using RF, you can trigger your camera from up to 328' away and without a line of sight limitation. The PROMASTER SystemPRO Wireless Remote Shutter Release allows you the freedom to operate your camera's shutter without having to touch or be near your camera. Unlike wireless infrared, this RF remote does not require line of