All Solenoid point motors require a brief burst of power to make them 'snap' across to firmly change the turnout blade.
Too longer burst of power could cause the solenoid to burnout.
If you use a 15v ac supply (usually provided as an accessory power feed from your controller) the solenoid will change over but it will also buzz like a hornet.
A DC power supply would need to supply a large current, increasing the risk of over heating the solenoid.
The PL-35 capacitor discharge unit provides the solution, it connects to the 15v ac accessory power feed and charges up a DC capacitor to provide a burst of clean power to power the solenoid.
The PL-35 is best used combined with the passing contact levers and solenoids shown below
