Decoder circuit for generating a system clock signal phase locked to a range tone signal

摘要

A decoder circuit for receiving a video input signal which includes Manchester coded data bits and a range tone component having a frequency of about 102.6 kilohertz. A phase lock loop circuit detects the presence of the 102.6 kilohertz range tone component and then generates a system clock signal which is phase locked to the range tone component of the video input signal. The system clock signal is provided to a clock generating circuit which generates a clock signal having four phases. The phase lock loop circuit also provides a logic signal which is supplied to a data detecting circuit allowing the data detecting circuit to convert the Manchester coded data bits to digital data bits.