Block Detectors 101

[Sumpter250]

The old system used light or IR sensors as detectors, but now I need to know what is needed to make this new block detector work.

Light, or IR sensors, are usually set up with a light / IR source ( emitter ), and they are "on" and drawing current from the
"crossing and signal system". When the light is "interrupted" the sensor stops drawing current, and it goes high/"1"/ true, and the signal system responds by lowering the gates. ( or changing the signal from green to red, however it is set up for )
Your "block detector" replaces that light/IR sensor (two outputs "to signal system" ). The Signal system provides the power, that the block detector uses.
The wire "from booster to track", carries track current. The "device" that the wire goes through is virtually a transformer.
When something draws track current, the "transformer", induces a current, in its secondary winding, that activates the "Output to the signal system", and the signal system does the rest.
Instead of sensing a light level change, this block detector senses track current changes. because of this it is more reliable.
With light detectors, the crossing gates could come down just because your hand blocked the light.
( or an "under the influence" LPB, fell on the detector !! :o )
Hope I've shed some "light" on the subject.