公开(公告)号：US3588719A

公开(公告)日：1971-06-28

申请号：US3588719D

申请日：1968-12-16

Applicant: IBM

Inventor： ABRAMSON PAUL ,  EMERSON LAWRENCE W

IPC: H03D3/16 ,  H04L27/14 ,  H04L27/148 ,  H03K9/00

CPC classification number: H04L27/14 ,  H03D3/16 ,  H04L27/148

Abstract: A FREQUENCY DETECTION SYSTEM FOR DETECTING THE FREQUENCY OF TONE SIGNAL BURSTS IS PROVIDED WITH A CONTROLLED DAMPING ARRANGEMENT TO LIMIT THE RESONANT BUILDUP OF THE TUNED FREQUENCY DEVICE EMPLOYED THEREIN. DAMPING IS IMPLEMENTED THROUGH UTILIZATION OF A THREE TERMINAL SIGNAL CONTROLLED VARIABLE IMPEDANCE DEVICE, SUCH AS AN FET DEVICE, WHEREIN THE VARIABLE IMPEDANCE PATH IS COUPLED IN SERIES WITH THE INPUT TO

THE SYSTEM AND THE CONTROL TERMINAL IS COUPLED TO THE OUTPUT OF THE SYSTEM.