The Ampetronic CTU11 is a Current Ratio Transformer, which can be used with an ILD1000G to optimise overall amplifcation. The CTU11 can often be used where the voltage or current demands of a loop would normally exceed the capabilities of the ILD1000G Loop Driver.

Thus unit is factory configured to maximise efficiency by matching the loop driver with the loop impedance; this avoids the need to specify two amplifiers as long as the Loop Driver has sufficient VA. The CTU11 can also be used to reduce loop current where both a small and large area needs to be driven with the same loop signal (such as in nave/chancel applications).