Using the emergency release the read head/switch can be unlocked manually. In the locked position of the emergency release, a ball detent mechanism prevents unintentional unlocking of the read head due to vibration or similar. In the unlocked position of the emergency release, an integrated bolt engages in a bore on the flange. To reset the emergency release, first the bolt must be pressed inwards, out of the detent mechanism, using a tool. Lead seal kit included.