公开(公告)号：GB2320994A

公开(公告)日：1998-07-08

申请号：GB9726216

申请日：1997-12-12

Applicant: IBM

Inventor： GOODNOW KENNETH JOSEPH ,  MICHAIL MICHEL SALIB ,  PRICER WILBUR DAVID ,  VENTRONE SEBASTIAN THEODORE

IPC: H04L1/24 ,  H04L25/34 ,  H04L25/49

Abstract: The invention relates to the use of calibration signals to correct multi-voltage level data signals. A multi-level data signal and a calibration signal representing the maximum possible amplitude of the data signal are sent from a first device 15 to a second device 30 in a network 10. The second device stores the calibration signal in unit 18, compares its amplitude to that of the data signal and corrects the data signal accordingly. Similarly, the calibration unit of the first device stores calibration signals corresponding to the other devices connected to the network and uses the appropriate calibration signal to correct signals received from these devices. Initially, the first device may inquire whether multi-level communication with a second device is possible and if not, revert to binary data signals. In this way, the system is able to automatically handle the transfer of signals to devices which are not multi-level compatible.

公开(公告)号：DE3879466T2

公开(公告)日：1993-09-16

申请号：DE3879466

申请日：1988-12-06

Applicant: IBM

Inventor： MICHAIL MICHEL SALIB ,  WALSH JAMES LEO

IPC: H03K19/00 ,  H03K19/082 ,  H03K19/086 ,  H03K17/16

Abstract: A half current switch comprising: at least one input transistor (16), a load resistance (42, 44) connected between a first voltage reference and the collector of the input transistor, a constant-current resistance (32) connected between the emitter of the input transistor and a second voltage reference, and a feedback means including at least one feedback connected to the constant-current resistance. The feedback means further includes means for biasing the feedback transistor (36) to drive a current through the constant current resistance (32) which, when flowing, increases with an increasing main current and decreases with a decreasing main current through the input transistor. The feedback means thus causes a constant current to be drawn by the input transistor (16) when it is conducting, thereby controlling the capacitance of the input transistor while maintaining the output level constant. In a preferred embodiment, the feedback means comprises a PNP transistor with its base connected t the collector of the input transistor, with its emitter connected to the first voltage reference, and with its collector connected to the emitter of the input transistor. The PNP transistor not only acts as a feedback device to control current, but also acts to prevent oscillations when a speed-up capacitor (54) is used in the circuit.