Rx is the resistance, there’s a lot of resistance in the circuit diagram, R1, R2…

Cx is non-polar capacitance, anti-interference capacitance of power input

IC integrated circuit module

Ux is IC

Kx is??? The component library definition varies from vendor to vendor

Tx is the test point (factory test)

Spk1 is a Speaker.

Qx is triode

Jx is Jack(like Audio Jack)

The component library definitions of Y1XXX vary from vendor to vendor

In addition, CEx- electrolytic capacitor, CNx- discharge (multiple capacitors together), RNx- exclusion, CONx- connector, Dx- bond, Hx- hole, JPx-Jumper, Lx- inductor/bead, LEDx- light emitting Diode, Xx- crystal oscillator.

Each manufacturer has his component library, the component that when drawing circuit diagram is pulled from library (big factory), to a few unusual, for instance CON, JP, each manufacturer definition also can differ somewhat

R (resistance)



CY(Y capacitor: high voltage ceramic capacitor, safety gauge)

CX(X capacitor: high voltage film capacitor, safety gauge)


C (capacitance)


ZD(voltage stabilizing diode)


U (IC)

J (jumper wire)

VR(adjustable resistor)

W regulator tube

K switch class

Y crystals

The serial Numbers of R107, C118, Q102 and D202 are often seen on the circuit board. Generally, the first letter identifies the device category, such as R for resistor, C for capacitor, D for diode and Q for three-stage tube. The second number is the function number of the circuit, such as “1” for the motherboard circuit, “2” for the power circuit and so on, which is determined by the circuit designer himself; The third and fourth digits represent the serial Numbers of similar devices on the circuit board.

R117: resistance on the main board, serial number 17.

T101: transformer on the main board.

SW102: switch

LED101: light-emitting diode

LAMP :(indicating) LAMP

Q104(E,B,C) : transistor, E: emitter,B: base,C: collector

“If R117 is a resistance, both ends should be connected with a multimeter.” it is not scientific to directly measure the resistance on the circuit board. The measurement result will be smaller than the actual value, or even much smaller.