TD-55 World's Smallest Transmitter Detector--- Absolutely the SMALLEST bug detector on the market. Suspicious of being watched or listened to by hidden cameras or audio bugs? You may be right, and the RF Bug Detector will prove you're NOT crazy by sniffing out hidden transmitters when placed within a few inches of the suspected item or person. Radio frequency signals (RF) are all around us and the World's Smallest Transmitter Detector provides a visual confirmation of this fact. This interesting little device gets excited when it detects RF and vigorously blinks chasing red lights when near almost any RF field. Size: Diameter= .8 in. , Height= .4 in. Runs on a commonly available lithium battery. This device can detect within the frequency range of 1MHZ to over 2GHZ. This device is not recommended for professional use but as a cost-conserving consumer device.