47 CFR §95.765

1. (a)Each RCRS transmitter type capable of transmitting on channels in the 72 or 75 MHz frequency band must be designed such that the carrier frequencies remain within ±20 parts-per-million (ppm) of the channel center frequencies listed in § 95.763(b) and (c) during normal operating conditions.
2. (b)Except as allowed under paragraph (c) of this section, each RCRS transmitter type capable of transmitting in the 26-28 MHz frequency band must be designed such that the carrier frequencies remain within ±50 ppm of the channel center frequencies listed in § 95.763(a) during normal operating conditions.
3. (c)Each RCRS transmitter type that transmits in the 26-28 MHz frequency band with a mean transmitter power of 2.5 W or less and is used solely by the operator to turn on and/or off a device at a remote location, other than a device used solely to attract attention, must be designed such that the carrier frequencies remain within ±100 ppm of the channel center frequencies listed in § 95.763(a) during normal operating conditions.