A key fob is a small token holding a proximity chip with a unique identifier. Held near a reader, it grants access according to the permissions attached to that holder. Fobs are quick, durable and easy to carry, but they can be lent or lost, so sensitive doors often demand a second factor.
The fob itself is only a number. What the system does with that number, and how quickly it can be canceled, is what protects the door.
Frequency and credential technology
Older 125 kHz fobs carry a fixed identifier that can be copied with inexpensive tools. A 13.56 MHz smart card can hold protected sectors and is the safer choice for new work.
Managing issue and return
Record who holds each fob, deactivate it on the day someone leaves, and reissue rather than share. An active fob in a drawer is an open door.