An audio-video distribution system includes a base station 12 having inputs and outputs for connection of audio-video sources and display screens respectively. In most embodiments, any audio-video source will be selectable for viewing on any display screen. Infra-red transmitters 14a,b,c,d are provided for controlling connected source devices and connected display screens. An application running on a mobile computer 16 can cause the infra-red transmitters 14a,b,c,d to transmit infra-red commands in response to user input. This is achieved with very low latency by loading machine code instructions into a secondary computer, and causing the second computer to execute those instructions in response to user input on the mobile computer 16. The machine code instructions can be stored on the mobile computer.