An operator ratchet mechanism for effecting reciproctable lateral movement if an element of a geared drive train in a door, gate or barrier operator. The operator ratchet mechanism can be utilised to cause disconnection between the geared drive train and an electric motor of the door gate or barrier operator to enable the door gate or barrier to me manually moved, and subsequent reconnection between the geared drive connection and electric motor. An embodiment of a tilt door operator which enables disconnection and reconnection between a geared drive train and an electric motor of the operator by effecting lateral displacement of an element of the geared drive train is also disclosed.