Main features & Overview


The GTT family of solid-state relays has been designed with the aim of providing very accurate control of the load from an analogue input signal (0-10V or 0-20/4-20mA) or a potentiometer (from 1kOhm to 10kOhm ).

The electronic design ensures that the cycle time for proportioning the power is automatically optimized.

The number of cycles that the GTT supplies to the load (fast cycling) for a given input signal is calculated to be the minimum possible to maintain the necessary accuracy.

This guarantees a very fast and accurate control loop that enables the GTT, driven by a controller or a PLC with analogue output, to obtain very precise control.

The GTT can be uses in three phase systems, using master-slave control architecture in which the control signal drives only one GTT (master) and this unit supplies the synchronized signals to the other units (slaves).

Optional monitoring for an interrupted load can be provided (HB).

This accepts a 500mAac input from a current transformer.

The trip point is adjustable with trimpots and there is LED indication and a normally open voltage free relay contact output.

The GTT solid-state relay has a green LED to indicate the presence of the 24Vac power supply and a red LED to indicate the switching state as a function of the input signal.

This LED will be continuously off for zero power and fully on at maximum and will flash at all intermediate values.

The units offer optional accessoires for panel mounting, fuses and fuseholders, current transformer and voltage transformer


Zero-voltage switching, optimised fast cycle time. Current range: 25A to 120A, diagnostics and load interrupt alarm

  • Command input from analogue voltage or current signal or potentiometer
  • Switching at voltage zero crossing
  • Partialization of wave train power with dynamically optimized time cycle
  • Antiparallel double SCR
  • 2 led for supply indication, “ON” state, 1 optional LED for load interrupt alarm
  • 4000V isolation between input circuit and power output
  • MOV (varistor)
  • Optional monitoring of interrupted load
  • DIN rail mounting (standard); Panel mounting (optional)


Gefran product range brochure
Power control
GTT datasheet
GTT Installation handbook


UL Certifications - UL - GS - GTS - GTT
UK Conformity declaration - GTT