abstract |
A structure is provided for accommodating the rotation of a front housing of an instrument to a selected position relative to the rear housing of the instrument to permit an operating member in the front housing to be located in a desired orientation. The front housing has an annular portion in which a cylindrical portion of the rear housing is received to permit the two housings to be rotated relative to each other about a common longitudinal axis. The front housing annular portion defines a plurality of bores arranged at selected azimuthal locations about the axis of rotation and the rear housing carries a reciprocative engaging member adapted to be moved partially into one of the bores to lock the two housings in a selected relative orientation. |