A wireless interface device for a keyboard of a computer system is achieved. The device comprises a radio transmitter and receiver. A modem encodes data to be sent by the radio transmitter and decodes data received by the radio receiver. A central processing unit is included. A direct signal connection is provided between the wireless interface circuit and a keyboard. A baseband circuit encrypts data to be transmitted and decrypts received data. The wireless interface device has built-in scanning and decoding functions for an input device such as a keyboard or a mouse. The wireless interface device has power saving functions to extend the battery life of the input device. The wireless interface device has the capability of automatically selecting between several communication frequencies or channels. The wireless interface device has the capability of automatically selecting between several data rates.