IBM 3174 Reference Manual page 207

L
L. Left.
LED. Light-emitting diode.
LF. Line feed.
LT. Logical terminal.
LU. Logical unit.
M
MLT. Multiple logical terminals,
modem. Modulator-demodulator.
MSR. Magnetic stripe reader.
N
NL. New Line.
No. Number.
NUL. Null.
NUM. Numeric.
O
OIA. Operator infromation area
P
PA. Program access
PAM. Printer authorization matrix.
PBX. Private branch exchange.
PC. Personal Computer.
PF. Picofarad.
PF. Program function.
PS. Programmed symbols.
R
Req. Request.
RTM. Response Time Monitor.
RTS. Request to send.
S
SA. Set attribute
SOS. SNA character string.
SI. Supress index
SNA. Systems Network Architecture.
SOH. Start-of-heading character.
SSCP. System services control point.
SIX. Start of text.
u
U.K. United Kingdom
U.S. United States.
X
XOFF. Transmitter off.
XON. Transmitter on.
X-2 3174 Establishment Controller Terminal User's Reference for Expanded Functions