The Datacryptor Link establishes secure point-to-point communications transparent to data protocols over private or public networks. The Link model is capable of synchronous data transmission at speeds up to 512 Kbps over RS-232, V.35 and V.11/X.21. The High Speed model is capable of data transmission on a framed or unframed T1/E1 interfaces at speeds up to 1.544/2.048 Mbps; 8Mbps over V.35 and X.21 in the case of the very high speed model. These units will also operate unframed over RS-232, V.35 and V.11/X.21 up to 8 Mbps with suitable 'smart' cables.