In general, the initial state of a Latching Relay is set by the manufacturer before use. For example, Panasonic Electric Works, TQ2SA-L2-12V-X’s initial condition is specified from the factory as shown below
But sometimes, you may find that this specified intitial state is changed before the relay is used. Does this mean the relay is defective?
The condition of arriving with the “reset” coil contacts in reset mode is not guaranteed and should not be considered as a defect. Latching relays are shipped from the factory in the reset stage, this is true. However, shock and impacts to the relay during shipping or installation may cause it to change its contact state.
For example, if an impact exceed 490 m/s² to our example relay, TQ2SA-L2-12V-X, that’s enough to cause the latching contacts to “switch over” and make connection in the “set” coil condition.
Because of this, it is recommended that the relay is used in a circuit which can initialize and force the relays into a reset condition prior to installation, if this is required by your design.