The Siemens 3RA1220-1DB23-0BW4 is a reversing combination starter in the SIRIUS family, frame size S0, rated for 2.2-3.2 A with a 24 VAC control voltage. It combines a reversing contactor pair and overload protection in a single Fastbus-mount package, saving panel space versus separate components. The 2.2-3.2 A range covers small reversing motor loads — conveyors, hoists, door drives — where forward/reverse cycling is needed. The 24 VAC control coil is common in control transformers stepped down from line voltage; verify your control circuit supplies clean 24 VAC, as brownout below the dropout threshold can cause chatter.
Frame size S0 occupies roughly 45 mm of DIN width; account for bending radius on the outgoing motor leads when laying out the gland plate. The 24 VAC control circuit draws coil inrush current typical of SIRIUS contactors — size the control transformer with enough VA headroom if multiple starters pick up simultaneously.