AG	Autopilot - General
AP	Autopilot - Magnetic

CC	Commputer - Programmed Calculator (outdated)
CD	Communications - Digital Selective Calling (DSC)
CM	Computer - Memory Data (outdated)
CS	Communications - Satellite
CT	Communications - Radio-Telephone (MF/HF)
CV	Communications - Radio-Telephone (VHF)
CX	Communications - Scanning Receiver

DE	DECCA Navigation
DF	Direction Finder

EC	Electronic Chart Display & Information System (ECDIS)
EP	Emergency Position Indicating Beacon (EPIRB)
ER	Engine Room Monitoring Systems

GP	Global Positioning System (GPS)

HC	Heading - Magnetic Compass
HE	Heading - North Seeking Gyro
HN   	Heading - Non North Seeking Gyro

II	Integrated Instrumentation
IN	Integrated Navigation

LA	Lorean A
LC	Lorean C

MP	Microwave Positioning System (outdated)

OM	OMEGA Navigation System
OS	Distress Alarm System (outdated)

RA	RADAR and/or ARPA

SD	Sounder, Depth
SN	Electronic Positioning System, other/general
SS	Sounder, Scanning

TI	Turn Rate Indicator
TR      TRANSIT Navigation System

VD	Velocity Sensor, Doppler, other/general
DM	Velocity Sensor, Speed Log, Water, Magnetic
VW	Velocity Sensor, Speed Log, Water, Mechanical

WI	Weather Instruments 

YC	Transducer - Temperature (outdated)
YD	Transducer - Displacement, Angular or Linear (outdated)
YF	Transducer - Frequency (outdated)
YL	Transducer - Level (outdated)
YP	Transducer - Pressure (outdated)
YR	Transducer - Flow Rate (outdated)
YT	Transducer - Tachometer (outdated)
YV	Transducer - Volume (outdated)
YX      Transducer

ZA	Timekeeper - Atomic Clock
ZC	Timekeeper - Chronometer
ZQ	Timekeeper - Quartz
ZV	Timekeeper - Radio Update, WWV or WWVH