Abstract: The system and method of the present invention provide a seamless approach for providing ATM connectivity for a Frame Relay DTE using an intelligent Terminal Adapter (TA). Using the system and method of the present invention, an enhanced Frame Relay protocol runs between the DTE and the ATM TA, the Frame Relay DTE is provided with not only the connectivity to the ATM network but also the full advantages of ATM transport mechanism. For instance, the FR DTE can choose to transmit its data using ATM Adaptation Layer (AAL) 1,3/4 or 5. Using the system and method of the present invention, a FR DTE may communicate with another FR DTE or to an ATM DTE through wide area or local area ATM network. The Frame Relay DTE can send data, image, voice, or video traffics across the ATM network via the FR/ATM terminal adapter.

Abstract: A terminal adapter interfaces between a Data Terminating Equipment (DTE) and either a Frame Relay or a Switched Multimegabit Data Service (SMDS) telecommunications network so that the type of network over which the DTE is communicating is transparent to the DTE. The terminal adapter performs mapping from one protocol to another so that a native frame relay DTE can access an SMDS network and so that a native SMDS DTE can access a frame relay network. The address mapping method performed by the terminal adapter uses a parallel table look-up technique which reduces the chance of collision (when two or more addresses hash into the same table entry), eliminates the traditional comparison function to detect a collision, and eliminates the traditional pointer technique when a collision occurs.

Abstract: A sensing apparatus for detecting impedance changes in a variable impedance matrix keyboard. A microcomputer is utilized to control the basic key intersection scanning and for accurately calibrating and adjusting the sensing threshold of the sense amplifier prior to testing each key intersection so that the effects of stray impedance and varying voltage levels may be compensated for. The micro computer supplies sense amplifier sensitivity threshold selection address codes to set the sensing level for the amplifier. Trial drive pulses are applied to a reference capacitor and are gated to the sense amplifier while the sensing level thereof is varied until no output is obtained. This effectively adjusts the sensing circuits for variable voltage power fluctuations occurring over a short time and compensates for variable capacitive effects not associated with actual key switch movements.