Proximity detectors with dual-speed tracking circuitry

A proximity detection arrangement of the type adapted for controlling the automatic opening and closing of a door, said proximity detection arrangement comprising:

• a sensor positioned to receive energy reflected from objects disposed in proximity to said door, said sensor providing a first electrical signal having a level responsive to the amplitude of said received energy;
• a tracking circuit arrangement connected to receive said first electrical signal, said tracking circuit arrangement generating a tracking electrical signal having a level which follows changes of a first direction and of a second direction opposite said first direction in the level of said first electrical signal, said tracking circuit causing said tracking electrical signal to follow first direction changes in said first electrical signal level substantially more rapidly than said tracking electrical signal follows second direction changes in said first electrical signal level;
• and
• a control circuit, operatively coupled to said sensor and to said tracking circuit arrangement, for controlling the opening and closing of said door in response to the difference between said first electrical signal level and said tracking electrical signal level.

A proximity detection arrangement for controlling a door to automatically open and close, said proximity detection arrangement comprising:

• sensor means for being mounted near said door so as to receive energy reflected from a zone in proximity to said door, said sensor means for providing an output signal responsive to said received energy, said output signal having a level;
• tracking means connected to receive said sensor means output signal, said tracking means for providing a further signal having a level which tracks changes in said sensor means output signal level, said tracking means including means for causing said further signal to follow increases in said sensor means output signal level at a first rate and for causing said further signal to follow decreases in said sensor means output signal level at a second rate substantially different from said first rate;
• and
• control means, operatively coupled to said sensor means and to said tracking means, for automatically opening and closing of said door in response to the difference between said sensor means output signal level and said further signal level.