PulseCode electronic locks use an encrypted 16-digit sequence of mechanical pulses transmitted when the user holds a PulseCode key against a solid surface, eliminating the need for direct contact between the lock and key. The opening code passes straight through to the lock, which opens if it hears the correct code. Each transmission is randomly encrypted, making it impossible to imitate the key, even if someone records the code. PulseCode by Master Lock. Circle 210.