An image signal supply system, including: a first image signal supply apparatus, a second image signal supply apparatus, and an image display apparatus, each of the first image signal supply apparatus and the second image signal supply apparatus outputting an image signal as an input source to the image display apparatus, the first image signal supply apparatus comprising: a communication unit carrying out communication with the image display apparatus; a switch receiving a predetermined operation; and a switching instruction output unit outputting an instruction signal to the image display apparatus via the communication unit on the basis of the predetermined operation performed on the switch, the image display apparatus including an input source switching unit disposed on the image display apparatus, the input source switching unit of the image display apparatus being configured to receive the instruction signal from the first image supply apparatus, characterized in that the instruction signal instructs the image display apparatus to switch the input source between the first image signal supply apparatus and the second image signal supply apparatus, the input source switching unit is adapted to switch the input source between the first image signal supply apparatus and the second image signal supply apparatus in response to the instruction signal, and each image signal supply apparatus (50, 90-92) is detachably connected to the image display apparatus. a first image signal supply apparatus, a second image signal supply apparatus, and an image display apparatus, each of the first image signal supply apparatus and the second image signal supply apparatus outputting an image signal as an input source to the image display apparatus, the first image signal supply apparatus comprising: a communication unit carrying out communication with the image display apparatus; a switch receiving a predetermined operation; and a switching instruction output unit outputting an instruction signal to the image display apparatus via the communication unit on the basis of the predetermined operation performed on the switch, a communication unit carrying out communication with the image display apparatus; a switch receiving a predetermined operation; and a switching instruction output unit outputting an instruction signal to the image display apparatus via the communication unit on the basis of the predetermined operation performed on the switch, the image display apparatus including an input source switching unit disposed on the image display apparatus, the input source switching unit of the image display apparatus being configured to receive the instruction signal from the first image supply apparatus, characterized in that the instruction signal instructs the image display apparatus to switch the input source between the first image signal supply apparatus and the second image signal supply apparatus, the input source switching unit is adapted to switch the input source between the first image signal supply apparatus and the second image signal supply apparatus in response to the instruction signal, and each image signal supply apparatus (50, 90-92) is detachably connected to the image display apparatus.