The groove defines a groove wall (20).

At the same time the block tumbler (BZ) with the counter tumbler (BG) in position (P1) also serve as coding tumblers.

The tube groove (64) is aligned with the flange groove (46).

A circumferential carrier groove is defined in the ring carrier, the carrier groove being concentric with the piston groove.

A flap (3) is designed to block the groove thereby locking the band (2) in the groove.

The throat end (28) is intubated into the throat (T) of the person (P) with the flaring helping create a seal within the throat (T).

The tube connector mates the flange groove (46) and the tube groove (64).

The distance between a part (20) of the relatively wide throat (19) from the relatively narrow throat (18) is greater than the distance between an opposing part (21) of the relatively wide throat (19) and the relatively narrow throat (18).

The groove (34) continuously extends in the circumferential direction, and the radius of the groove is constant.

The tumbler may be stimulated by an impulse of mechanical energy, and, after stimulating the tumbler, the vibrational response of the tumbler may be detected over a period of time.

The finger can extend toward the throat and is adapted to retain the flexible member within the throat.

The radius (C') of the gullet (13') is larger than 1/2 of the depth (D') of the gullet (13').

The air groove is provided on the rear body, a rising boss is provided on the bottom surface of the groove.

The magnet retention slot is formed such that movement of the permanent magnet towards at least one end of the slot will tend to cause the magnet to become wedged within the slot.

According to the invention, the ratio of the groove widths (Bn2) at the groove openings (37) to the groove widths (Bn1) at the respective groove base (36) lies in the range of 0.69 to 0.81, preferably in the range of 0.73 to 0.78.