140 Commonly Used PCB Markings

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PCB Markings

Printed circuit boards, or PCBs, are a vital component of electronic devices, as they provide a platform for electrical components to be connected and communicate. To ensure that the PCBs are installed and laid out correctly, various markings are used to indicate where specific components should be placed. There are approximately 140 common PCB markings, each with its own distinct meaning. Understanding the purpose of these markings is essential to getting the most out of a PCB. With this knowledge, you can ensure that your PCB is laid out correctly and that all components are installed in the right places.

Meaning of the Different PCB Markings

Letters CodeMeaning
AATautomatic power-on device
ACalternating current
DCdirect current
HPlight plate
KDdifferential relay
KFflasher relay
KHthermal relay
KMintermediate relay
KOFexport intermediate relay
KSsignal relay
KTtime relay
KVvoltage relay
KPPolarization Relay
KRReed Relays
KIimpedance relay
KAmomentary relay
QFcircuit breaker
QSisolation switch
TAcurrent transformer
TVvoltage transformer
WDC bus
PQSactive and reactive apparent power
EUIelectromotive voltage current
SEexperiment button
Qcircuit switching device
FRthermal relay
SBpush button switch
SAtransfer switch
PJActive energy meter
PJRReactive energy meter
PFFrequency table
PPAPhase Meter
PMMaximum Demand Meter (Load Monitor)
PPFPower Factor Meter
PWActive power meter
PRReactive power meter
PARReactive ammeter
HAAcoustic signal
HSOptical signal
HLIndicator light
HRRed light
HGGreen light
HYYellow light
HBblue light
HWWhite light
XBConnection piece
XTTerminal board
WBDC bus
WIBPlug-in (feed) bus
WPPower branch line
WLLighting branch line
WEEmergency lighting branch line
WPMPower mains
WLMLighting mains
WEMEmergency lighting mains
WTtrolley line
WCLClosing small busbar
WCControl small busbar
WSSignal small busbar
WFFlash small busbar
WFSAccident Sound Small Bus
WPSForecast audio small bus
WVVoltage small busbar
WELMEmergency Lighting Small Busbar
FTFFast Fuse
FFDropout fuse
FVVoltage limiting protection device
SBPPressure switch
SBTTest button
SBRReverse button
SBSStop button
SBEPanic button
SGSignal lamp
SLLevel switch
SMHumidity control switch
SPPressure control switch
SQLimit switch
SQPProximity switch
SRReset button
SSSpeed control switch
STTemperature control switch auxiliary switch
SVVoltmeter changeover switch
SWAutomatic transfer switch
TBPPressure transmitter
TFTemperature limiter
TMTemperature transmitter
TTTemperature controller
UBUninterruptible power supply
URThyristor rectifier
USSoft starter
UTStep-down transformer
VFrequency converter
VCControl circuit with power rectifier
BVspeed changer
BT1BKTime measuring sensor
BLLiquid level sensor
BHBMTemperature measurement sensor

Tips for Reading PCB Markings

Reading the markings on a printed circuit board (PCB) can be daunting at first, but with some practice and basic knowledge of the symbols and codes used, it can become second nature. Here are some tips to help you get started:

Learn the basic symbols and codes

Familiarize yourself with the most common symbols and codes used on PCBs, such as component designators, polarity indicators, reference designators, and rating markings. Knowing these will help you understand the information on the board more easily.

Read the component labels

Component labels usually include a manufacturer’s part number, a description of the component, and the electrical characteristics of that component. This information will help you identify what type of component is installed on the board and its specifications.

Inspect the board closely

Take your time when inspecting the board to look for any signs of damage or corrosion. Look for any solder joints that may have been disturbed, and any components that may have been added or removed from the board.

Refer to the schematic

If you’re having trouble understanding the markings on the board, refer to the schematic to cross-reference the markings and make sure they match up. This can help you determine if there are any discrepancies between the board and the schematic.

Test the components

Once you’ve identified the components on the board, test them to make sure they’re working correctly. This will help you confirm that the board is functioning properly and is free of defects.

Read the markings from left to right

When reading a PCB marking, it is important to read the markings from left to right, as this will help to ensure accuracy. This is especially important when there are multiple components in a single line.

Look for additional information

In some cases, additional information may be included on the PCB markings. For example, the maximum voltage or current rating of a component may be included. It is important to look for this information in order to ensure that the component is suitable for its intended purpose.

Use a reference guide

If you are having difficulty interpreting a PCB marking, it can be helpful to consult a reference guide. A reference guide will provide detailed information about the various symbols and abbreviations used in PCB markings, as well as their meaning.


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Aidan Taylor

I am Aidan Taylor and I have over 10 years of experience in the field of PCB Reverse Engineering, PCB design and IC Unlock.

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