Alternate field luminance enhancement in a spectrum conserving television system

In a television bandwidth compression system of the type which allows two television programs to simultaneously utilize the bandwidth allowed for one television program, said television bandwidth compression system including a transmitter connected to receive composite video signals from each of first and second program sources, each of said video signals supplying chrominance information, luminance information and synchronization and timing signals, and providing an output signal wherein chrominance information for said first and second program sources is sent on alternate lines of each image frame for each program, respectively, during the normal horizontal retrace time and the luminance information for both program sources is sent during the active video time for each line of each image frame for each program, respectively, and further including a receiver for receiving said output signal from said transmitter and providing an output composite video signal of a selected program from said first or second program sources, the improvement wherein the luminance bandwidths of alternate fields of a television picture are limited to high and low values, said improvement comprising:

• in the transmitter, first and second signal processor means responsive, respectively, to said first and second program sources for providing as output signals separated chrominance, luminance and synchronizing signals, each of said first and second video processor means, respectively, including first switched low pass filter means connected to receive said separated lumninance signals and, during alternate fields, passing said separated luminance signals as high and low bandwidth limited luminance signals;
• and
• in the receiver, second switched low pass filter means connected to receive said high and low bandwidth limited luminance signals of a selected program in the output signal produced by said transmitter and, during each field, passing a selected one of said high and low bandwidth-limited luminance signals, respectively, in alternate sequence, in synchronism with the selected one of said high and low bandwidth limited luminance signals passed by said first switched low pass filter means.