Abstract: An anti-reverse mechanism for a central dictation record-playback machine comprises an anti-reverse solenoid, a normally open contact, mechanism for activating the anti-reverse solenoid and a device connected to the contact which precludes backspacing of a recording tape relative to a record-playback head of a central dictation record-playback machine when the contact is closed. The anti-reverse solenoid has a movable arm which is connected to a plate on which a record medium index is slidably mounted and driven along the plate by a worm gear. The plate is adapted to pivot about its longitudinal axis to disengage the index from the worm gear. Upon such disengagement, the index returns to its start position on the plate to close the contact whereby backspacing into previously recorded messages on the dictation machine is precluded.