With the increased threat of terrorism, many public places – including synagogues, study halls, and yeshivot – have guards stationed at the entrance with a hand-held metal detector, checking everybody who enters for a weapon (which usually registers as a large block of metal). Regretfully, this is also necessary on Shabbat and the holidays. But there is a problem: when metal is detected, an electric circuit is turned on which sounds a buzzer or vibrates the device.
To solve this dilemma, The Zomet Institute has developed a metal detector in which no electric circuit is turned on or off. A mechanism that causes very low-level vibrations (as in a cellphone) is left on for the entire Shabbat, and if the device is brought close to metal the level of vibration increases. The prohibitions related to operating electrical devices on Shabbat ("giving birth" to a new current, lighting a flame, or construction) are relevant only if a current is turned on or off but not if the level of current is changed.
This hand-held device may be used on Shabbat even according to the most stringent halachic requirements. It has been approved by Chief Rabbi Amar and Rabbi Neubirt (author of "Shemirat Shabbat K'Hilchato").
Since low-level vibrations must persist throughout Shabbat, this device can only work when connected to a power source and not from batteries.
The Zomet Institute has also developed Metal Detecting Gates for Shabbat, which are in use at the entrances to such places as the Western Wall, government offices, and malls.
For details and prices, contact The Zomet Institute.