Detection of stamps on documents

Claim 1

A CIRCUIT ARRANGEMENT TO DETERMINE THE STAMPED CONDITION OF AN ENVELOPE OR DOCUMENT REGARDLESS OF THE BACKGROUND REFLECTANCE OF THE ENVELOPE AS COMPARED WITH THE REFLECTANCE OF A STAMP HAVING A CERTAIN NUMBER OF REFLECTANCE VARIATIONS BELOW AN OPTIMUM REFLECTANCE VALUE COMPRISING: MEANS TO GENERATE A SIGNAL VOLTAGE PROPORTIONAL TO THE SUCCESSIVE REFLECTANCE VALUES OF A PORTION OF SAID ENVELOPE ON WHICH A STAMP MAY BE NORMALLY PLACED; MEANS TO APPLY SAID VOLTAGE SIMULTANEOUSLY TO THE INPUTS OF A FIRST CIRCUIT HAVING A FIRST STORAGE DEVICE AND A SECOND CIRCUIT HAVING A SECOND STORAGE DEVICE INCLUDING A BISTABLE DEVICE; MEANS IN SAID FIRST CIRCUIT TO STORE INFORMATION IN SAID FIRST STORAGE DEVICE ONLY WHEN SAID SIGNAL CONTAINS REFLECTANCE VALUES LOWER THAN SAID OPTIUM REFLECTANCE VALUE FOR PREDETERMINED TIME PERIOD; A SECOND MEANS IN SAID SECOND CIRCUIT TO STORE INFORMATION IN SAID SECOND STORAGE DEVICE ONLY WHEN SAID SIGNAL CONTAINS SAID CERTAIN NUMBER OF VARIATIONS IN REFLECTANCE VALUES EXCEEDING A GIVEN RANGE IN A TIME PERIOD SUBSTANTIALLY EQUAL TO SAID FIRST MENTIONED PERDETERMINED TIME PERIOD; MEANS CONNECTING THE OUTPUT OF EACH OF SAID STORAGE DEVICES TO AN AND GATE WHEREBY THE SIMULTANEOUS OCCURRENCE OF INFORMATION IN SAID DEVICES PRODUCES A SIGNAL IN THE OUTPUT OF SAID AND GATE TO INDICATE THE STAMPED CONDITION OF SAID ENVELOPE.