1
Master element
2
Time delay starting or closing
3
Checking or interlocking relay
4
Master contactor
5
Stopping device
6
Starting circuit breaker
7
Anode circuit breaker
8
Control power disconnect device
9
Reversing device
10
Unit sequence switch
11
Not used
12
Overspeed device
13
Synchronous speed device
14
Under speed device
15
Speed or frequency matching device
16
Not used
17
Shunting or discharge switch
18
Accelerating or decelerating device
19
Starting to running transition contactor
20
Electrically operated valve
21
Distance relay
22
Equalizer circuit breaker
23
Temperature control device
24
Not used