Although cell phones are probably the most useful communications devices ever developed (until now, that is), they do tend to get a little bit on a person's nerves, especially when they are outfitted with some very obnoxious ringtones. And that's exactly the reason why the people over at DealExtreme have come up with the Personal Cell Phone Signal Blocker Device back in August 2007, as this rather unusual product can block the cell phone signal on a 0.5 – 12 meter area around it.
According to the vendors, the jammer uses super-high frequency and mini power interference technology in order to block the GSM signals by interrupting the downlink connections without affecting in any way the handhelds.
It would seem that this device is quite effective, since it can block CDMA/GSM 869-960 Mhz networks, 2110-2170 Mhz 3G networks and 1805-1920 MHz DCS/PHS networks. The “circle of no-communication” created around the device has a variable radius, depending on the type of carrier network and other factors, but, nevertheless, it extends to a minimum radius of around 0.5 meters.
Moreover, the device is not dangerous for the human body (maximum level of emitted EM radiation is less than -10dBm), and requires relatively little power in order to operate, since a full-charge of the built-in 1500mAh battery lasts for up to 3 - 4 hours of continuous use. It's encased in a solid, shockproof metal casing and it's also extremely portable, as it measures around 4.09 inches x 1.85 inches x 0.71 inches (10.4 cm x 4.7 cm x 1.80 cm), at a weight of around 6 ounces (170 grams).
The device presented by DealExtreme retails for around 50 US dollars, which is a rather fair price to pay for such a device, despite the fact that this thing is of Chinese origins, so its efficiency is not exactly guaranteed.