Secure Terminal Equipment

STE is designed to use ISDN telephone lines which offer higher speeds of up to 128 kbit/s and are all digital.

The greater bandwidth allows higher quality voice and can also be utilized for data and fax transmission through a built-in RS-232 port.

[1] STE sets look like ordinary high-end office desk telephones and can place unsecured calls to anywhere on the public switched telephone network (PSTN), as well as secured calls on it via the phone's backwards compatible STU-III mode.

When an NSA configured Crypto Card is present, secure calls can be placed to other STE phones.

[2] As of 2007, a typical STE terminal cost about $3,100, not including the crypto card.