A = Assembly B = Fan BT = Battery C = Capacitor CB = Circuit Breaker 4-1 CR = Diode D = Diode DL = Delay Line DS = Lamp E = Terminal F = Fuse FL = Filter J = Connector, Recept K = Relay L = Inductor M = Meter P = Connector, Plug Q = Transistor, Semiconductor R = Resistor, Potentiometer RT = Temperature Sensing Element S = Switch T = Transformer TB = Terminal Block TP = Test Point U = Integrated Circuit V = Vacuum Tube, Neon Bulb, Photocell, etc. VR = Zener Diode W = Wire, Cable X = Socket Y = Crystal Unit