14 CFR §171.29

1. (a)The facility must be installed according to accepted good engineering practices, applicable electric and safety codes, and FCC licensing requirements.
2. (b)The facility must have a reliable source of suitable primary power.
3. (c)Dual transmitting equipment may be required to support some IFR procedures.
4. (d)A facility intended for use as an instrument approach aid for an airport must have or be supplemented by (depending on the circumstances) the following ground-air or landline communications services:
   1. (1)At facilities outside of and not immediately adjacent to controlled airspace, there must be ground-air communications from the airport served by the facility. Voice on the aid controlled from the airport is acceptable.
   2. (2)At facilities within or immediately adjacent to controlled airspace, there must be the ground-air communications required by paragraph (d)(1) of this section and reliable communications (at least a landline telephone) from the airport to the nearest FAA air traffic control or communication facility.