According to §74.1283 of the regulations:
Translators can be identified through voice announcements within specific time frames: between 7-9 am, 12:55-1:05 pm, and 4-6 pm, broadcast over the primary station.
Translators can also be identified by transmitting the call sign in international Morse code. This can be achieved through modulation with a minimum of 30 percent modulation and using a frequency that is not within 200 kHz of the old EBS attention signal frequencies. Alternatively, the translator can identify itself through frequency shift keying, which involves a carrier shift between 5 and 25 kHz.