Locks on doors, safes, cabinets, etc. can be unlocked in a variety of ways.
You are probably most familiar with the common metal key. These come in a variety of styles, which is probably why there are many collectors of keys. Combination locks are used on safes and doors–clockwise to 23, counterclockwise to 42, clockwise to…, or you punch in a certain sequence of numbers or letters on a keypad. Sometimes a safe is unlocked electronically at a certain time. Your computer may be “locked” with a password or it is equipped to recognize your finger print. A safe in a “Lovejoy” episode unlocked when it recognized the proper retinal pattern of the user. Bill Nighy got frustrated in “Page Eight” when his key-card wasn’t recognized by the lock at MI 5. Perhaps you’ve suffered the same frustration trying to get into your room at a motel.
The Centaurian Bud Vase, in my novel of the same name, could be used as a “key” in three different ways. You’ll have to read the novel when/if it’s published to find out how.
A scent activated lock was introduced in the “Ghost Writer in the Sky” chapter of my novel, Silver Threads:
Baroo smiled, turned back to the safe, and exhaled slowly against the chemical
sensor of the lock. He turned the handle, pulled the door of the safe open, and
retrieved the stack of paper wrapped in the blue ribbon.
Scent activated locks are based on lab-on-a-chip technology. A microchip contains a gas chromatograph, mass spectrometer, dielectric spectrometer, or some similar analytic tool or combination of tools, a microprocessor, memory, and other necessary electronics. Scent activated locks were initially used on safes, but can also be used on homes, businesses, and vehicles.
To train the lock to the desired “combination”, the user breathes gently on the chemical sensor region of the lock on the exterior of the door. The contents of the breath are analyzed, classified, and presented to the user on a screen on the inside of the door. Obvious “red herring” readings can be deselected, leaving a mix of chemicals unique to the biochemistry of the user. For instance, if Baroo had taken a drink of Roo’eft wine (as he did in “Ghost Writer in the Sky”) before beginning the lock’s training, he might want to eliminate the wine’s chemistry from the combination. Or, maybe not–Perhaps Baroo wants the lock to recognize him only if he has Roo’eft wine on his breath. Repeating the procedure over several days would allow the program of the lock to recognize the chemicals unique to the user.
Information about the user’s species allows the lock’s program to recognize her even as she ages or suffers from some illness.
If desired, the lock could be trained to recognize several users so that members of a family or employees of a business could all open a door or start a vehicle.
Keep reading/keep writing – Jack