Bi-stable and Monostable Electronic Lock for Automatic Sliding Door

About the Electronic Locks for automatic sliding doors, there are 2 key types called bi-stable and single-stable(monostable),here's a clear explanation of the differences between these 2 locks as below .

▪ Bi-stable Electronic Lock

Definition: Has two stable states - Locked or Unlocked.

State Change: Requires an active electronic pulse (like a button press, valid credential scan, relay signal) to switch from one state to the other (e.g., from Locked to Unlocked, or from Unlocked to Locked).

Power Dependency: Maintains its current state (Locked or Unlocked) even during a complete loss of power. It "remembers" its last commanded state.

Mechanism: Typically uses a latching relay or a bi-stable solenoid/motor. These mechanisms physically lock into position until actively changed.

Common Use Cases: Main entry doors, doors where security must be maintained during power failures (remains locked), or doors that need to stay unlocked during a power failure (remains unlocked). Often requires separate signals for "Lock" and "Unlock".

Power Failure Behavior: Fails-Secure OR Fails-Safe (depending on last commanded state): Stays locked if last commanded state was Locked; stays unlocked if last commanded state was Unlocked.

▪ Single-stable/Monostable Electronic Lock

Definition: Has only one stable state (usually Locked) and one unstable state (Unlocked).

State Change: Requires continuous power to hold the Unlocked state (the unstable state). Removing power automatically causes it to revert to its stable state (Locked).

Power Dependency: Requires constant power to remain unlocked. Loss of power causes an automatic return to the Locked state.

Mechanism: Typically uses a standard (non-latching) solenoid. Power applied pulls the bolt back (unlocks); removing power releases the solenoid, allowing a spring to return the bolt to the locked position.

Common Use Cases: Fire exits (must unlock automatically on power loss for egress), stairwell doors, panic bars, or any door where automatic locking on power failure is critical for safety or security.

Power Failure Behavior: Fails-Safe (to Locked): Automatically locks when power is removed. (Note: In fire exit contexts, "Fail-Safe" often means unlocking on power loss - achieved by wiring the lock so power is applied to lock it, and removed to unlock it. This is a specific configuration of the monostable principle).