 wave, shall not exceed the amounts indicated below at any value of APL (average picture level) between 10% and 90%: Short haul Medium haul Satellite Long haul End-to-end Based on ANSI/EIA/TIA-250C (Ref. 6). 16.7.5 Signal-to-Noise Ratio (10 kHz to 5 MHz) The video signal-to-noise ratio is the ratio of the total luminance signal level (100 IRE units) to the weighted rms noise level. The noise referred to is predominantly thermal noise in the 10-kHz to 5.0-MHz range. Synchronizing signals are not included in the measurement. The EIA states that there is a difference of less than 1 dB between 525-line systems and 625-line systems. As stated in the ANSI/EIA/TIA 250C standard (Ref. 6), the signal-to-noise ratio shall not be less than the following: Short haul 67 dB Medium haul 60 dB Satellite 56 dB Long haul 54 dB End-to-end 54 dB and, for the low-frequency range (0-10 kHz), the signal-to-noise ratio shall not be less than the following: Short haul 53 dB Medium haul 48 dB Satellite 50 dB Long haul 44 dB End-to-end 43 dB TELEVISION TRANSMISSION 16.7.6 Continuity Pilot A continuity pilot tone is inserted above the TV baseband at 8.5 MHz. This is a constant amplitude signal used to actuate an automatic gain control circuit in the far-end FM receiver to maintain signal level fairly uniform. It may also be used to actuate an alarm when the pilot is lost. The normal TV baseband signal cannot be used for this purpose because of its widely varying amplitude. 16.8 TV TRANSMISSION BY SATELLITE RELAY TV satellite relay is widely used throughout the world. In fact, it is estimated that better than three-quarters of the transponder bandwidth over North America is dedicated to TV relay. These satellite facilities serve CATV headends,6 6 hotel/motel TV service, for TV broadcasters providing country, continental, and worldwide coverage for networks, TV news coverage, and SO on. As we discussed in Section 16.9.3, a satellite transponder is nothing more than an RF repeater. This means that the TV signal degrades but little due to the t