Electronic control system for monitoring and controlling the movement of an envelope through a mail sorting machine

In a mail sorting machine having a plurality of deflecting gates which are arranged in pairs to provide a single guideway through which envelopes may be asynchronously conveyed, each deflecting gate having a normal position in which an envelope is allowed to pass through said guideway unimpeded and a deflect position in which an envelope is deflected out of said guideway, the improvement therein of a tracking circuit associated with each pair of deflecting gates and interconnected in series with the remaining tracking circuits, each tracking circuit serving to control the position of the gates, each successive tracking circuit comprising:

• sensing means for generating an alert signal in response to an approaching envelope;
• means for accepting from a preceding tracking circuit an encoded designation signal in response to an alert signal, said designation signal being arranged to have a location portion which is encoded to represent a particular numerical value and an encoded gate designating portion;
• each tracking circuit for a succeeding pair of gates including means for generating and transmitting a clear signal to the tracking circuit of the immediately preceding pair of gates to clear the designation signal therefrom upon the acceptance of said encoded designation signal by said tracking circuit for a succeeding pair of gates and irrespective of the elapsed time of movement of an envelope between adjacent pairs of gates as sensed by successive tracking circuits;
• means for changing the numerical value of said location portion of said designation signal by a set numerical quantity to thereby produce an updated designation signal;
• means for comparing the numerical value represented by the location portion of the new designation signal with a preselected numerical value;
• and
• means for examining the gate designating portion of said new designation signal if the numerical value represented by the location portion of the updated designation signal coincides with said preselected numerical value, said examining means also being operable to cause the deflecting gate designated by the gate designating portion of said updated designation signal to be placed in a deflect position.