What is "xermx-oc"

Radio México Internacional is a Mexican government-run radio service based in Mexico City. It broadcast as a shortwave radio station with the broadcast callsign XERMX-OC from 1969 to 2004, and was relaunched as an Internet-only radio service in 2011. Since 1983 it has been under the control of the Instituto Mexicano de la Radio (IMER). The -OC suffix is from onda corta, Spanish for "short wave", equivalent to the -SW suffix in Canada (with none being used at all on U.S. shortwave stations).