Mag lock
A mag lock, also known as a magnetic lock is a security latch for gates that uses electricity to power an electromagnet, which locks and unlocks the mag lock depending on whether there is current coming through a switch or not.
Mag locks are often used on entrance gates that have intercom systems, and a button on the intercom acts as the switch to unlock the gate for visitors, but other types of wired pushbuttons and wireless remote controls can also be used.