Patent ID: 8320564

Claim:
An encrypted signal detection circuit to detect encrypted messages in video signals and output stable trigger control signals, the encrypted signal detection circuit comprising: an amplifier circuit to amplify the video signals; wherein the video signals are divided into positive phase video data signals, negative phase synchronization pulse signals, and encrypted signals, and the encrypted messages are carried in the encrypted signals a separation circuit to extract negative phase pulse signals from the amplified video signals, wherein the negative phase pulse signals comprise negative phase encrypted signals and the negative phase synchronization pulse signals; a reverse circuit to reverse the extracted negative phase pulse signals and output positive phase pulse signals; a delay circuit to delay duty cycles of the positive phase pulse signals and output the delayed positive phase pulse signals; and a trigger circuit to output stable trigger control signals based on the delayed positive phase pulse signals; wherein the amplifier circuit comprises: an amplifier comprising a positive input to receive the video signals, a negative input grounded via a first resistor, and an output to output the amplified video signals; a second resistor connected between the negative input and output of the amplifier; wherein the first and the second resistors are arranged to detect an amplification coefficient of the amplifier circuit.