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
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L24: 24th Inductor on the board


D108: 108th Diode on the board
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Common Designator Meanings:
Wikipedia Source

Designator Component type
A Separable assembly or sub-assembly (e.g. printed circuit assembly)
AT Attenuator or isolator
BR Bridge rectifier
BT Battery
C Capacitor
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 or oscillator
GN General network
H Hardware, e.g., screws, nuts, washers
HY Circulator or 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 or contactor
L Inductor or coil or ferrite bead
LS Loudspeaker or buzzer
M Motor
MK Microphone
MP Mechanical part (including screws and fasteners)
OP Opto-isolator
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
RN Resistor network
RT Thermistor
RV Varistor, Variable resistor
S Switch (all types, including buttons)
T Transformer
TC Thermocouple
TP Test point
TUN Tuner
U Integrated circuit (IC)
V Vacuum tube
VR Voltage regulator (voltage reference), Variable resistor (potentiometer or rheostat)
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.)
XTAL Crystal
Y Crystal or oscillator
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