SIK, SOK and CCK keys are provided that are enough like those designed for Tymnet so as to serve those programs we know of that are designed to use Tymnet style SIK3, SOK3 and CCK3 keys.
PADPF is a factory that accepts an X.25 circuit key and returns SIK, SOK and CCK keys. There should be an X.3 pad at the other end of the X.25 circuit. TCEMK is not provided because few programs use it and the TCEMK functions are not available from X.3 pads.
PADPF also provides the PAD function directly so to let some kind of terminal already connected to the system play the role of a combined X.3 pad and start-stop ASCII terminal.
Upon expiration of the circuit by signal from the circuit or from either SIK, SOK or CCK, a message is sent via the key FIN thus:
cause-code is 0 for clear indication from CK, 1 for kt+1 from SIK, 2 for kt+1 from SOK and 3 for order code 4 on the CCK.
Note that DK(0) serves as FIN if no report is required.