Rectified 230VAC to 24VDC
A few thoughts:

There's no capacitor in there.  Remember that the AC voltage drops to zero twice every cycle of the mains.
A &quot;capacitive dropper&quot;, using a capacitor to limit the current, would generate a lot less heat than a big resistor.  It's a very common circuit design, often used for driving LED lamps.
The circuit may generate an apparently safe 24V, but it's directly connected to the mains.  Assume everything is live and insulate accordingly.