This is the Bueler BU510TD time delay ON relay. A 12 volt, 20/30 amp SPDT (single pole, dual throw) relay with a built-in adjustable timer.

Delay ON means the circuit waits before switching, adjustable from 2 seconds up to 3 minutes. The classic use is stopping amplifier turn-on pop by holding the amp back until the head unit has settled, but it applies anywhere a circuit needs to come up after something else.

This is the third generation, redesigned around what installers asked for: a top-access adjuster you can reach once it's mounted, a waterproof body, and a 340 degree potentiometer for finer control.

Specifications

• 12 volt DC, operating range 8 to 15 volts
• 20 amp / 30 amp rated contacts
• SPDT, single pole dual throw
• Delay ON, adjustable 2 seconds to 3 minutes
• Low 1 volt (1k ohm) trigger
• Internal green LED indicator
• Waterproof, standard automotive relay format

Need the circuit to stay on after the trigger stops instead? That's the BU509TD delay OFF.