H04M11/00
Telephonic communication systems specially adapted for combination with other electrical systems
H04M11/00
Telephonic communication systems specially adapted for combination with other electrical systems
H04M11/06
Simultaneous speech and data transmission, e.g. telegraphic transmission over the same conductors
H04M11/06
Simultaneous speech and data transmission, e.g. telegraphic transmission over the same conductors