1. The board is made of 1.6MM high-quality FR-4 board with tin spraying. The relay is , and the resistance is all It is a -ring gold film copper pinresistor. And it has a power indicator light, the relay will suck for about 3 seconds after power on , the indicator green light is on, and the work indication function. 2. The voltage used by this protection board is a single power supply AC 12-18V, which can be powered from the power amplifier board Just take a electricity. Conditional try to use winding or separate power supply 3. This protection board can be used with 1875 power amplifier board, or with LM3886, TDA7294, TDA7293 and other matching use. 4. All finished boards are debugged and tested with electricity. 5. PCB size: 80x50M Finished speaker protection board for three-channel power amplifier board Colour:blue Material:plastic Package Contents: 1 x Speaker Protection Board Only the above package content, other products are not included. Note: Light reflection and different displays may cause the color of the item in the a little different from the real thing. The measurement allowed error is +/- 1-3cm.