Population Estimates and the Needs of Local Governments

A control device for controlling the switching operation between a scanner having built-in printer port to which a printer is connected and the printer is disclosed. The control device has a computer connector for connection with the parallel port of the computer to receive control bus signals, status bus signals and data bus signals therefrom. The control bus and status bus signals are applied to the printer and the scanner through latches and tri-state buffers which are controlled respectively by the scanner and the printer. The two control units receive the data bus signals from the computer and perform decoding operation on the data received to enable/disable the latches and tri-state buffers so as to activate/de-activate the printer and scanner. The control device initially activates the printer with the scanner off, storing the control signals on the control bus of the computer, sending a first data signal to the control units to latch the control bus and status bus from the computer to the printer, sending a second data signal to the control units to open the control bus and status to the scanner, sending a third data signal to the control units to latch the control bus and the status bus to the scanner when a scanning operation is done, and sending a fourth data signal to the control units to release the control bus and status bus to the printer to activate the printer again.