To provide a pulse transmission line control system that can prevent a malfunction of microcomputers included in an apparatus configured by the microcomputers that have a function of decoding an electrical signal pulse generated from an infrared code sent from an infrared remote control unit. A main microcomputer A (1) controls on/off states of a switch (6) provided in a pulse transmission line (5) and turns on the switch (6) only when a sub-microcomputer B(2) performs a process on the infrared code sent form an infrared remote control unit (3).