To surely output an alarm to illegal dismount and to stop an alarm output function in normal dismount work by providing a tag device with a release capable of setting up an unlock signal to an output state and holding a locking mechanism so as to detach the other end of a string body from a case.

When a self-ringing burglary prevention tag is gradually inserted into an insertion space 49 of the release 39, an unlock signal outputting switch 57 is driven at first. Thereby a CPU is functioned and an alarm output inhibition command radio wave is outputted by a transmission coil 55. The radio wave is received by a self-ringing burglary prevention tag side antenna, so that an alarm output ringing function is stopped. Then the tag is furthermore inserted into the space 49, a pair of release pins 41, 43 erected on the side of the release 39 are inserted into insertion holes 35, 37 formed on the tag side. Consequently a releasing operation detection switch 45 arranged on the tag side is driven and the start of releasing operation is detected.