Facsimile signal modification reducing the information channel bandwidth
Abstract
Abstract IT HAS BEEN FOUND THAT TYPICAL FACSIMILE SIGNALS DERIVED FROM SCANNING BLACK COPY ON A WHITE BACKGROUND CAN BE PROCESSED IN SUCH A WAY AS TO SUBSTANTIALLY REDUCE THE COMMUNICATION CHANNEL BANDWIDTH REQUIRED TO TRANSMIT A GIVEN AMOUNT OF INFORMATION. IN THE TYPICAL SYSTEM TO BE DESCRIBED THE BANDWIDTH IS REDUCED BY A FACTOR OF TWO TO ONE. PULSES OF MODULATED SUBCARRIER FROM A FACSIMILE SCANNER ARE PROCESSED TO FORM A THREE LEVEL SIGNAL HAVING ONE-HALF THE REPETITION RATE OR FREQUENCY OF THE ORIGINAL SIGNALS AND HENCE ONE-HALF THE FREQUENCY BANDWIDTH. THESE REDUCED BANDWIDTH SIGNALS ARE TRANSMITTED OVER THE COMMUNICATION CHANNEL. AT THE RECEIVING END THE REDUCED BANDWIDTH SIGNALS ARE PROCESSED TO RESTORE THEIR ORIGINAL FORM AND ARE THEN APPLIED TO A FACSIMILE RECORDER. THIS INVENTION PERMITS EITHER TWICE THE INFORMATION TO BE SENT OVER A GIVEN CHANNEL OF RESTRICTED BANDWIDTH OR TO SEND THE SAME AMOUNT OF INFORMATION OVER A CHANNEL HAVING ONE-HALF THE BANDWIDTH.
Inventors
- 👤 John H Clark
- 👤 Rene C Bache
Bibliographic Details
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