A very useful abbreviation Code guide for Telex devices.

Abbreviation Codes

ABFF Answerback Format faulty.
ABS Absent. (Office closed).
ANUL Delete.
BK I cut off.
CFM Confirm.
CLG Calling.
COL Collation please/I collate.
CRV How do you receive?/I receive well.
DER Dérangé. (Out of order)

DF You are in communication with the called telex service.
GA Go ahead/You may transmit.
INF Customer temporarily unobtainable.
IFE Office closed because of holiday.
MNS Minutes.
MOM Wait a moment please.
MUT Mutilation.
N A Correspondence to this international destination is not admitted.
NA Not Admitted. (Correspondence to this service is not admitted).
NC No circuits.
N C No circuits (International).
NCH Number has been changed.
NI No line identification available.
NP No Plant. (The called number is not, or is no longer a telex service).
N P The called international number has been typed incorrectly.
NR Indicate your number/My number is..
OCC Occupé. (Distant equipment occupied).
PPPP Stop transmission.
PPR Paper.
R Received.
RAP Rappel. (I shall call you back).
RPT Repeat/I repeat.
SSSS Here ready for data transmission.
SVP Sivousplait – Please.
TAX What is the charge/The charge is..
TESTMSG Please send a test message.
THRU You are now connected with a telex terminal.
TPR Teleprinter.
W Words.
WRU Who are you?
XXXXX Error.
+ + End of transmission acknowledgement not required.
+? End of transmission, you may transmit.

Source : http://members.iinet.net.au/~oseagram/telex1.html