O Glossary Terms - O Offline Lock A lock that is not connected to the access control system and must be updated manually. OHMS The measure of resistance of an electrical device to the flow of electricity. OHMS Law Relationship of voltage, current and resistance in a circuit, E = I x R. (where E is voltage, I is current, and R is resistance). Online Lock A lock that is constantly connected to the access control system (typically through an access control panel). Open Back Strike For use with a pair of doors. The back of the strike is cut away, permitting the inactive door to be opened independently. Opening Force Force required to open a door against the closers spring power. OSDP Open Supervised Device Protocol is the latest Access Control industry standard for hard-wired reader communications. OSDP is an RS-485, bi-directional protocol that can both support encryption and higher data speeds than its predecessor (Wiegand) as well as longer distances (4000 ft.).