hi someone can help me to analysis this circuit? when Rpot is 1k and I start to reduce pot value the relay change condition((ON)) when Rpot= 275ohm and when I increase Rpot relay comeback unchange mode((off)) in 500ohm ,this operation it's okay to me but if I put Rpot = 470 ohm and start to reduce the Rpot the relay is on mode why??? and why does designer put Re2,Rb1,Rb2 ??? when I pick up Re2 my hysteresis change??