The number of terminals between a camera and an attachment can be reduced by a new combination of camera and attachment. The combination comprises first and second terminals for connecting the attachment to the camera; an information signal generating circuit on either one of the camera or the attachment for generating in time series first and second information signals and for transmitting said first and second signals to the other one through the first terminal; first and second responding circuits on the other one and operable in response to the first and second information signals respectively; a switchover signal generating circuit provided on the one for generating a switchover signal and for transmitting the signal to the other one through the second terminal; and a switchover circuit for transmitting the first and second information signals coming through the first terminal to the first and second responding circuits selectively in accordance with the switchover signal coming through the second terminal.