Frame synchronizer and a signal switching apparatus

A signal switching apparatus for selecting an output signal from at least one local television signal composed of frames and an external television signal composed of frames, wherein the external television signal is a wide screen oriented high definition television signal having a main screen signal and a support signal for improving image quality of the high definition television signal, said signal switching apparatus comprising:

• a switching means having at least one input terminal for receiving the local television signal, at least one additional input terminal, and an output terminal,
• a frame synchronizer having an input terminal for receiving the external television signal and an output terminal connected to said additional input terminal of the switching means, said frame synchronizer including a memory, a read/write control means for detecting frame difference between the external television signal and the local television signal and for writing the external television signal into the memory and reading the external television signal from the memory after a predetermined delay that depends on said frame difference, and a low pass filter that receives the support signal that is read out from the memory when the frame difference is at least one frame, and
• a control means for controlling said switching means and said frame synchronizer.

A frame synchronizer for receiving an external color television signal composed of frames and a local color television signal composed of frames and at least approximately synchronizing a color frame of the external television signal with a color frame of the local television signal, wherein the external television signal is a wide screen oriented high definition television signal having a main screen signal and a support signal for improving image quality of the high definition television signal, said frame synchronizer comprising:

• a memory,
• a read/write control means for detecting color frame difference between the external television signal and the local television signal and for writing the external television signal into the memory and reading the external television signal from the memory after a predetermined delay that depends on said color frame difference, and
• a low pass filter that receives the support signal that is read out from the memory when the color frame difference is at least one frame.

A signal switching apparatus for selecting an output signal from at least one local color television signal composed of frames and an external color television signal composed of frames, wherein the external television signal is a wide screen oriented high definition television signal having a main screen signal and a support signal for improving image quality of the high definition television signal, said signal switching apparatus comprising:

• a switching means having at least one input terminal for receiving the local television signal, at least one additional input terminal, and an output terminal,
• a frame synchronizer having an input terminal for receiving the external television signal and an output terminal connected to said additional input terminal of the switching means, said frame synchronizer including a memory, a read/write control means for detecting color frame difference between the external television signal and the local television signal and for writing the external television signal into the memory and reading the external television signal from the memory after a predetermined delay that depends on said color frame difference, and a low pass filter that receives the support signal that is read out from the memory when the color frame difference is at least one frame, and
• a control means for controlling said switching means and said frame synchronizer.