AT = Actuating time setting	EV = Emergency trip valve
A = Acceleration command setting	SA = Servo amplifier
B = Release command setting	SV = Servo valve
T = Tachogenerator	C = Caliper unit
DI = Differentiating network	D = Brake disc
I = Integrating network	S = Brake command switch, normally closed
E = Acceleration, error detector	= Summing symbol