DTL regulator is a mainly unit of DDZ-Ⅱ series instrument. It accepts 0～10mA DC signal from transmitter or converter and compare with inner given value or external given value. The result will be Proportional integral and differential operate by regulator and send 0～10mA DC signal to actuator.

There are two types of instrument. DTL-221A、321A、121A is mainly applied on petrochemical field. It has two input channels. One is main channel and the other is vice channel. The panel is formed with a Deviation shows header, a Scale dial, hand-operation dial and a 0～10mA DC current indicator. DTL-331A、231A、154A is mainly applied in power field. There are 4～5 channels without manual operation.

DTL-154A、331A have an independent differential channels.

DTL-221A、321A、231A、331 are large deviation meter.(Indicating controller)