... : 7 KHz 6,audio frequency: 400 Hz current work: 12 DCV "AA" (alkaline) 8X1.5V 7 ... This product using voice alarm and instrumentation, with the probing depth exploration of metal the size, shape, weight, have ... the contrary, The smaller the area, the fewer the number, the smaller the corresponding depth. The following table lists the most probing depth, the enterprise is based on standard products with ...