China Mobile and China Unicom are available in domestic, and can intercommunicate. Not only that, you can make an encrypted call through the operators abroad, as long as the coding rate is the same as GSM/WCDMA above 8Kb/s.

The EVRC vocoder with a maximum speed of only 8Kb/s is adopted by the Telecom coding standard CDMA/CDMA2000, which will produce larger compression distortion to the encrypted voice waveform modulated by RLSpeakTM technique, and there will be a high error rate after demodulating by RLSpeakTM again. So China Telecom is not available temporarily.