Abstract: A battery-cover lock mechanism for portable apparatus includes a housing (5) having an operating-battery receiving region (5a) and a backup-battery receiving region (5b) and two separate covers (2, 3) for each region. The housing (5) further includes a slidable lock button (4) that is movable in an L-shaped path and that effects motion of a lock lever (6) that in one position (FIG. 6) by means of tongues (7, 8) locks both covers (2, 3); in a second position (FIG. 5), locks only one cover (2); and in a third position (FIG. 4) locks only the other cover (3). In an alternative embodiment (FIGS. 7 and 8), a sensor rod (17) is included for preventing removal of the back-up battery cover (3) when an operating battery (12) is not present.