75 Hz track circuit receiver

The 75 Hz electronic receiver is the train detection element of coded track circuits. It detects whether the track is clear or occupied and recognises insulation failures of the insulated rail joints separating consecutive block sections.

The receiver takes a filtered track signal and a reference signal at its input. Its internal electronics evaluate the level and the relationship of these signals and drive the connected relay as its output.

Advantages

• purely electronic design with no moving parts
• can drive a class 1 track relay directly
• also detects short circuits across the insulated rail joint

Technical data

• Size, mounting: single-width rack unit
• Supply voltage: 220 V +10…−20%, 75 Hz
• Input impedance: 0.8…1.3 kΩ
• Track-side sensitivity: 3.1 ± 0.1 V rms
• Reference-side sensitivity: 165–170 V rms

References

• Around 4,500 units in operation in automatic block and station interlocking systems – the most widely used track occupancy detection device on the lines of MÁV and GySEV.