PURPOSE: To inform immediately brake interruption to a program in a computer, by depressing a brake key of a terminal equipment by using a brake response signal, a brake sequence signal and a brake text signal.

CONSTITUTION: If the brake key of the terminal equipment is depressed when the terminal equipment is in receiving data from the computer, the terminal equipment returns a brake response signal to the computer and the computer sends an EOT signal to the terminal equipment to release a data link. If the brake key of the terminal equipment is depressed during an idling period, the terminal equipment sends a brake sequence signal to the computer, the computer responds to the terminal equipment by an ACK signal and then the terminal equipment sends an EOT signal to the computer to release the data ink. If the brake key of the terminal equipment is depressed during the data transmission from the terminal equipment to the computer, the terminal equipment transmits a brake text signal to the computer at the reception of the response of the ACK signal from the computer, receives the ACK signal from the computer and then transmits an EOT signal to the computer to release the data link.