49 C.F.R. § 220.27 – Identification.

(a) Except as provided in paragraph (c) of this section, the identification of each wayside, base or yard station shall include at least the following minimum elements, stated in the order listed:
1. (1) Name of railroad. An abbreviated name or initial letters of the railroad may be used where the name or initials are in general usage and are understood in the railroad industry; and
2. (2) Name and location of office or other unique designation.
(b) Except as provided in paragraph (c) of this section, the identification of each mobile station shall consist of the following elements, stated in the order listed:
1. (1) Name of railroad. An abbreviated name or initial letters of the railroad may be used where the name or initial letters are in general usage and are understood in the railroad industry;
2. (2) Train name (number), if one has been assigned, or other appropriate unit designation; and
3. (3) When necessary, the word “locomotive”, “motorcar”, or other unique identifier which indicates to the listener the precise mobile transmitting station.
(c) If positive identification is achieved in connection with switching, classification, and similar operations wholly within a yard, fixed and mobile units may use short identification after the initial transmission and acknowledgment consistent with applicable Federal Communications Commission regulations governing “Station Identification”.