Abstract: A television signal transmission system comprises a headend including a pair of SAW filters having equal delays, one filter having amplitude and normalized phase versus frequency response characteristics continuously varying between about -6 db and 180 degrees at the picture carrier frequency and zero db and zero degrees at the sound carrier frequency of the television signal, the second filter having substantially flat amplitude and normalized phase responses between the picture and sound carrier frequencies. An RF video signal is applied to both filters, the output of the first filter being selected for transmission during at least a portion of the horizontal blanking intervals of the television signal with the output of the second filter otherwise being selected for transmission. The transmitted signal is received by a decoder including a bi-phase stable phase modulation detector and third and fourth SAW filters having response characteristics complementary to the headend filters.

Abstract: In a cable television (CATV) system improved upstream data communication is provided by the use of preferred frequencies. Harmonics of downstream video and audio carrier signals arising from cable discontinuities produce common mode nonlinear distortion. Cable discontinuities caused by a loose, defective or corroded connector operate as a downstream mixing diode. The cross- and intermodulation products thus produced are avoided in the present invention by the use of upstream frequencies displaced from these harmonics. In a preferred embodiment, two harmonically-related upstream carriers generated by a single signal source and centered between adjacent harmonic noise peaks provide reliable upstream data channels in a two-way CATV system. In another arrangement, each subscriber terminal transmits upstream in an alternating manner, first at one frequency and then at a second frequency, until an acknowledge signal is received from the CATV headend.