Amplifier design technique has made it possible to provide a usable band of about 18 MHz while still keeping the repeater spacing of about 4.5 km as defined in Recommendation G.332; the CCITT has therefore defined an 18 MHz system which offers a transmitting capacity of 3600 telephone channels in the case of pure telephone application. Alternatively, the system may be used for the transmission of up to two TV channels or one TV signal plus 1800 telephone channels. Another possibility is that the bandwidth above 12 435 kHz could be used for the provision of an 8448 kbit/s digital path.
ITU-T G.334 SPANISH-1993 Referenced Document
ITU-T J.77 CHARACTERISTICS OF THE TELEVISION SIGNALS TRANSMITTED OVER 18 MHz AND 60-MHz SYSTEMS