47 C.F.R. § 95.215 (R/C Rule 15) Do I have to limit the length of my communications?
Title 47 - Telecommunication
(a) You must limit your R/C communications to the minimum practical time. (b) The only time your R/C communications may be a continuous signal for more than 3 minutes is when operation of the device requires at least one or more changes during each minute of the communications. (c) Your R/C station may transmit a continuous signal without modulation only if: (1) You are using it to operate a model aircraft device; and (2) The presence or absence of the signal operates the device. (d) If you show that you need a continuous signal to insure the immediate safety of life of property, the FCC may make an exception to the limitations in this rule.
Title 47: Telecommunication
PART 95—PERSONAL RADIO SERVICES
Subpart C—Radio Control (R/C) Radio Service
How To Operate an R/C Station
§ 95.215 (R/C Rule 15) Do I have to limit the length of my communications?

