CPC G07C 9/00309 (2013.01) [G07C 2009/00793 (2013.01); G07C 2209/63 (2013.01)] | 11 Claims |
1. A method for determining whether a portable key device is located inside or outside a metal door, the method being performed by a credential communication device and comprising:
obtaining a first time-of-flight, ToF, measurement between a first antenna and the portable key device, wherein the first antenna is located on the outside of the metal door;
obtaining a second ToF measurement between a second antenna and the portable key device, wherein the second antenna is located on the inside of the metal door; and
determining the portable key device to be located on the outside of the metal door when the first ToF measurement is less than the second ToF measurement by an amount which is greater than a threshold value.
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