SlingSecure Phones can be split in two main categories: 2G and 3G:

SlingSecure 2G phones make use of the GSM standard mobile channel, which means that it establishes the secure connection through a CSD data channel which most mobile operators provide free on their lines.

Mobile 2

SlingSecure 3G phones make use of 3rd generation internet mobile connections such as UMTS, GPRS or even Wi-Fi, establishing an encrypted voice connection through a proprietary Internet Data Protocols similar to VoIP (Voice over IP).