Patent ID: 6704416
Filing Date: 2004-03-09
Classification: H04M

Abstract:
A hook switch status glitch filter circuit for use on a line card, the line card having a positive voltage operational power feed and a connection to ground, said glitch filter circuit comprising:a voltage divider network formed by a first and a second resistor and connected between the positive voltage operational power feed and the connection to ground and having a midpoint connection that provides an intermediate voltage; a first comparator receiving a circuit input signal at its positive voltage input connection and receiving said intermediate voltage at its negative voltage input connection, and connected to the positive voltage operational power feed at its supply voltage connection, and connected to the connection to ground at its ground connection; a third resistor connected at one end to the output of said first comparator; a fourth resistor connected at one end to the positive voltage operational power feed and connected at the other end to the other end of said third resistor; a first capacitor connected at one end to the connection to ground and connected at the other end to said other end of said third resistor and to said other end of said fourth resistor; and a second comparator connected at its positive voltage input connection to said other end of said first capacitor and to said other end of said third resistor and to said other end of said fourth resistor, and connected at its negative voltage input connection to said intermediate voltage, and providing a circuit output signal at its output connection, and connected to the positive voltage operational power feed at its supply voltage connection, and connected to the connection to ground at its ground connection.