H ELECTRICITY
H04 ELECTRIC COMMUNICATION TECHNIQUE
H04B TRANSMISSION
H04B1/00 Details of transmission systems, not covered by a single one of groups H04B3/00 - H04B13/00; Details of transmission systems not characterised by the medium used for transmission
H04B1/38 Transceivers, i.e. devices in which transmitter and receiver form a structural unit and in which at least one part is used for functions of transmitting and receiving
H04B1/54 using the same frequency for two directions of communication