Schematic Symbols

• Single Cell - a single DC battery cell of 0.5V

  
• DC Battery Supply - collection of single cells forming a DC battery supply

  
• DC Voltage Source - a constant DC voltage supply of a fixed value

  
• DC Current Source - constant DC current supply of a fixed value

  
• Controlled Voltage Source - dependent voltage source controlled by an external voltage or current

  
• Controlled Current Source - dependent current source controlled by an external voltage or current.

  
• AC Voltage Source - a sinusoidal voltage source or generator

  
• Earth Ground - referencing a common zero potential point

  
• Chassis Ground - connected to the power supplies earthing pin

  
• Digital Ground - common digital logic circuit ground line

  
• Fixed Resistor - whose resistive value is indicated next to its schematic symbol

  
• Potentiometer - Three terminal resistance whos resistive value is adjustable from zero to its maximum value

  
• Rheostat - two terminal fully adjustable rheostat whos resistive value varies from zero to a maximum value

  
• Trimmer Resistor - small variable resistors for mounting onto pcbs

  
• Thermistor - resistive value changes with changes in surrounding temperature

  
• Fixed Value Capacitor - capacitive value is indicated next to its schematic symbol

  
• Polarize Capacitor - usually an electrolytic capacitor which must be connected to the supply as indicated

  
• Variable Capacitor - adjustable capacitor whose capacitance value can be varied by the means of adjustable plates

  
• Open Inductor - coil or solenoid generates a magnetic field around itself when energised

  
• Iron Core Conductor - formed by winding the coil around a solid laminated iron core indicated by solid lines

  
• Ferrite Core Inductor - formed by winding the coil around a non-solid ferrite core indicated by dashes lines.

  
• SPST Toggle Switch - single-pole single-throw toggle used for making (ON) or breaking (OFF) a circuits current

  
• SPDT Changeover switch - single-pole double-throw changeover switch used for changing the direction of current flow from one terminal to another

  
• Pushbutton Switch (N.O) - normally open contacts pushbutton switch, push to close release to open

  
• Pushbutton Switch (N.C) - normally closed contacts pushbutton to switch, push to open, release to close.

  
• SPST Relay Contacts - electromechanical relay with internal single-pole single-throw toggle contacts

  
• SPDT Relay Contacts - electromechanical relay with internal single-pole double-throw changeover contacts

  
• DPST Relay Contacts - electromechanical relay with internal double-pole double-throw changeover contacts

  
• DPDT Relay Contacts - electromechanical relay with internal double-pole double-throw changeover contacts

  
• DIP Switch Assembly - PCB mounted with 1-to-10 toggle switches either single-pole, double-pole, rotary or with a common terminal

  
• Semiconductor Diode - semiconductor pn-junction diode used for rectification and high current applications

  
• Zener Diode - used in its reverse voltage breakdown region for voltage limiting and regulation applications

  
• Schottky Diode - consisting of an n-type semiconductor and metal electrode junction for low voltage applications

  
• NPN Bipolar Transistor - lightly doped p-type base region between two n-type emitter and collector regions with the arrow indicating direction of conventional current flow out

  
• PNP Bipolar Transistor - lightly doped n-type base region between two p-type emitter and collector regions. indicates direction of conventional current flow in

  
• Darlington Pair Transistor- two bipolar transistor npn or pnp connected in a series common collector configuration to increase current gain