SX440 is a half-wave phase-controlled thyristor type Automatic Voltage Regulator(AVR) and forms part of the excitation system for a brushless alternator.

Technical specification
Input
Voltage 190~260VAC
Frequency 50~60Hz
Output
Voltage Max 90VDC at 207VAC input
Current Continuous 4ADC
Intermittent 6A for 10 secs
Resistance 15 ohms minimum
Regulation +/- 1.0% 

We also have

R230, R250, R438, R448, R449,

SX460, SX440, AS440, MX341, MX321,

SR7,

UVR6,

SE350,

M16FA655A, M40FA640A/A,

VR6/K65-12B.