Costs more than trigger locks or chamber locks. A push-button keypad, combination, or key opens the lock. May not prevent theft, as some locks may be removed later. A device that blocks the chamber to prevent a cartridge from being fired. A comination lock or key opens the lock.
Some models have anti-tamper alarms.
Any locking device that is part of hte handgun and allows only the owner to operate it. Another uses a combination lock in the grip of the handgun or the magazine that holds the cartridges. Other designs using radio signals are under development. May contain magnetic or electronic components. Quick to immediate access.