Siemens sirius digital speed monitoring relay spdt co din rail siemens 3ug4651 1aw30 this relay is a digital speed monitoring relay with a range of 0 1 to 2200 rpm with suitable sensor features an lcd display wide ac dc control voltage range fault storage facility external auto and manual resets and adjustable startup and tripping delays siemens 3ug4651 1aw30 speed monitoring relay digital spdt co