LiTZ is an acronym for Long-interval Tone Zero. Used in communications, especially in Ham Radio. If an operator has an emergency, they press and hold the zero key while transmitting for 3 full seconds. This activates the receivers of other Hams who have compatible radios for LiTZ. This gets people on the repeater to assist with the emergency.
If the victim of the emergency cannot speak, they can key their microphones every minute to allow other hams to find their position using techniques developed with foxhunting, where other amateur radio operators use portable radio equipment to zero in via triangulation on the exact position of the victim.