This holds the first of eight possible 192-bit Triple DES receive decryption keys, entered as a 48-character hex string. Because encryption is one-directional per key set, with transmit keys encrypting outgoing traffic and receive keys decrypting incoming traffic, this receive key must match whatever key the far-end modem used to encrypt the traffic it is sending, independent of what this unit uses in its own transmit keys. If the far-end modem transmits using its key3 slot, this unit's receiveKey1 slot must be loaded with that exact same key value for the incoming traffic to decrypt correctly, even though the local slot numbers do not need to match.