PCB Markings: Reference Designator Meanings (Part Identification)

Most circuit boards will have a reference designator listed by each part. These represent the component type and placement location on the board. Looking at the reference designator by a faulty component will help point you in the right direction to what type of part you are requiring.

Example Designators:

C20: 20th Capacitor on the board

L24: 24th Inductor on the board

D108: 108th Diode on the board

Common Designator Meanings:

Designator Component type
A Separable assembly, Sub-assembly (e.g. printed circuit assembly)
AN, AS Antenna
AR Amplifier
AT Attenuator, Isolator
BR Bridge rectifier
B, BT Battery
BZ Buzzer
C Capacitor
CB Circuit breaker, Supercapacitor
CN Capacitor network
D, CR Diode (all types, including LED), Thyristor
DL Delay line
DS Display, General light source, Lamp, Signal light
F Fuse
FB Ferrite bead
FD Fiducial
FL Filter
G Generator, Oscillator
GN General network
H Hardware, Screws, Nuts, Washers
HY Circulator, Directional coupler
IR Infrared diode
J Jack (least-movable connector of a connector pair), Jack connector (connector may have male pin contacts and/or female socket contacts)
JP Jumper (Link)
K Relay, Contactor
L Inductor, Coil, Ferrite bead
LS Loudspeaker, Buzzer
M Mosfet, Motor, Meter, Measuring device
MH Mounting hole
MK Microphone
MP Mechanical part (including screws and fasteners)
OP Opto-isolator, Operational amplifier
P Plug (most-movable connector of a connector pair), Plug connector (connector may have male pin contacts and/or female socket contacts)
PS Power supply
Q Transistor (all types)
R Resistor
RLA, RY Relay
RN Resistor network
RT Thermistor
RV Varistor, Variable resistor
S, SW Switch (all types, including buttons)
T Transformer, Triac, Incorrectly used as transistor (see “Q”)
TC Thermocouple
TP Test point
TR Transistor, Transducer
TUN Tuner
U Integrated circuit (IC), Inseparable assembly
V Vacuum tube
VR Voltage regulator (voltage reference), Variable resistor (potentiometer or rheostat), PTC
W Cable, Wire, Busbar
X Socket connector for another item not P or J, paired with the letter symbol for that item (XV for vacuum tube socket, XF for fuse holder, XA for printed circuit assembly connector, XU for integrated circuit connector, XDS for light socket, etc.)
XMER Transformer
XTAL Crystal
Y Crystal, Oscillator
Z Zener Diode

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