Elevator position sensing system using coded vertical tape

An elevator position sensing system, comprising:

• a tape vertically mounted in an elevator shaft;
• the tape having two parallel tracks of indicia running along its length, the first track of indicia comprising a pseudo-random code sequence having an N-bit code length which is non-repeating for any N successive bits along the length of the tape, and in which each N-bit length of code represents a coarse elevator position, the spacing between successive coarse elevator positions being equal to the spacing between successive bits in the code;
• the second track of indicia comprising a fine code track for generating fine position information between successive coarse elevator positions in the first track;
• a sensor unit mounted on the elevator car having first and second sets of sensors aligned with the respective first and second tracks of indicia for detecting the indicia in each track and for producing corresponding coarse and fine code output signals as the sensor unit moves along the tape, the first set of sensors comprising means for producing an N-bit coarse position code output each time the unit traverses one-bit length of the first track;
• and
• output means connected to said sensor outputs for detecting said output signals and converting them to elevator car position data for transmission to an elevator controller at predetermined intervals.