I - odpowiednio - "circulating/rotating one".
"A straight ring counter or Overbeck counter connects the output of the last shift register to the first shift register input and circulates a single one (or zero) bit around the ring. For example, in a 4-register one-hot counter, with initial register values of 1000, the repeating pattern is: 1000, 0100, 0010, 0001, 1000... . Note that one of the registers must be pre-loaded with a 1 (or 0) in order to operate properly."
https://en.wikipedia.org/wiki/Ring_counter
"A multiple NAND gate 67 inserts a single zero into the ring counter 42, to provide the circulating zero for use as the timing signal to apply the tach pulse to the shift register 30. When the zero is in the final output position in the ring counter 42(...)"
http://www.google.pl/patents/US4140896
Tutaj "rotating zero":
http://tinyurl.com/qdmog9r
Tutaj oba terminy:
"However, with the resistors in place, a rotating zero is sent to the inverter inputs. The zero represents the direction of the wind. The "circulating zero" is changed into a "circulating one" by use of the inverters. "
https://repositories.tdl.org/ttu-ir/bitstream/handle/2346/10...