A portable radio telephone (5) communicates with base stations (1, 2) in a digital radio telephone system, such as DECT, employing TDMA transmission. The portable radio telephone is programmed with an algorithm which is operative to select a communication channel by storing a blind slot mask (7)...http://www.google.de/patents/US5825757?utm_source=gb-gplus-sharePatent US5825757 - Methods and apparatus for excluding communication channels in a radio telephone 
