Section 74.720 - Digital low power TV distributed transmission systems(a) A digital low power TV or TV translator (LPTV) station may be authorized to operate multiple synchronized transmitters on its assigned channel to provide service consistent with the requirements of this section. Such operation is called a distributed transmission system (DTS). Except as expressly provided in this section, LPTV stations operating a DTS facility must comply with all rules in this part applicable to LPTV single-transmitter stations.(b) For purposes of compliance with this section, a digital LPTV station's "authorized facility" is the facility authorized for the station in a license or construction permit for non-DTS, single-transmitter-location operation. A digital LPTV station's "authorized service area" is defined as the area within its protected contour (described by § 74.792 ) as determined using the authorized facility.(c) The protected area for each DTS transmitter is determined based on the F(50,90) field strength given in § 74.792 ), calculated in accordance with § 73.625(b) of this chapter. The combined protected area of an LPTV DTS station is the logical union of the protected areas of all DTS transmitters, that falls within the station's authorized service area as defined in paragraph (b) of this section.(d) The DTS limiting area for each DTS transmitter is determined using the field strength from § 74.792 and the F(50,50) curves.(e) An application proposing use of DTS will not be accepted for filing unless it meets all of the following conditions:(1) The combined protected area covers all of the applicant's authorized service area;(2) Each DTS transmitter's LPTV DTS limiting contour falls within the authorized facility's LPTV DTS limiting contour;(3) Each DTS transmitter's protected area is contiguous with at least one other DTS transmitter's protected area;(4) The "combined field strength" of all DTS transmitters in a network does not cause interference to another station in excess of the criteria specified in § 74.793 . The combined field strength at a given location is determined by a "root-sum-square" calculation, in which the combined field strength is equal to the square root of the sum of the squared field strengths from each transmitter in the DTS network at that location; and(5) Each DTS transmitter must be located within the station's authorized service area.(f) All transmitters operating under a single LPTV DTS license must follow the same digital broadcast television transmission standard. 86 FR 21227 , Apr. 22, 2021