Secure Terminal Equipment (STE) is the U.S. government's current and encrypted telephone communications system for wired communications (as of 2008[update]).
It is designed to use ISDN telephone lines. It offers higher speeds of up to 128 Kbit/s. The greater bandwidth allows higher quality voice. They also can also be used for data and fax transmission through a built-in RS-232 port.
STE is intended to replace the older STU-III office system and the KY-68 tactical system.[1][2]
Office: The Office STE (most widely used STE) provides voice and data access to ISDN (Integrated Services Digital Network) and PSTN (Public Switched Telephone Network) telecommunications systems.
Tactical: The Tactical STE is similar to the Office STE but can also access the TRI-TAC (TRI Service TACtical) network. It has a serial EIA-530A/EIA-232 BDI (Black Digital Interface) port.
Data: The Data STE provides remote access for voice, fax, data and video-conferencing. This model has two serial EIA-530A/EIA-232 BDI ports. It also allows for data transfers to multiple destinations.
C2: The C2 STE is similar to the Tactical STE but C2 has modified software for use with its Tactical Terminal Locking Handset mechanism.
STE-R: Similar to the Data STE, the STE-Remote provides dial-in access to the Defense Red Switch Network (DRSN).
VoIP: The STE now has Voice over Internet Protocol (VoIP) capability, available as an upgrade to the current models, or built into some new models.