Abstract: A control and switching unit used with at least two devices for transmitting information or voice communication over telephone lines. The control and switching unit is provided with a series of relays to ensure that only one of the devices receives or transmits information at any one time. A timing circuit is utilized such that if one of the devices is a telephone, the second device would not be able to gain access to the telephone line if the telephone is ringing. Additionally, if the telephone is in use, the secondary device, such as a modem, could be selected and this secondary device would gain access to the telephone line after the use of the telephone has been discontinued.