Holmes Electric Time Lock Co.

This lock had an electrical system fed by low voltage batteries which would, in case of failure of both time lock movements, unlock the mechanism. The lock could be set for day or night operation. Case #21, movement #350. c. mid 1880's.

This is an example of a rare subset of time locks. So called 'transitional' time locks. These were produced for a brief period of time during the early development of the time lock when the reliability of the mechanical watch movements were not fully trusted. So a secondary way of unlocking the vault door was devised in case of their failure. Soon it was realized that this was not necessary as the movements rarely failed and with the fact that they were devised with at least one or two (later sometimes three) redundant movements the chances of complete failure becomes very remote. The very fact that a way to override the time lock existed in these transitional models, violated the basic purpose of the time lock concept - that the door could not be opened under any circumstances before the appointed time. For another example of such a transitional lock see the Consolidated time lock combined with an emergency secret combination lock here. file 63