WMATA uses {so called} high frequency AC track signaling. I'm told this works without insulated rail gaps [except at interlockings], and I'm looking for a write up on exactly how it does so.
I'm a EE & know the basics, you apply AC of a given frequency to one WeeZ bond, and look for it on the one at the other end of the block. An axle will shunt the rails, and the relay drops. The next block uses a different frequency. [WMATA uses 4 on a given track: 12341234 etc.]
But what keeps Block B from dropping when the wheelset is still in A, or even further away? I assume the reuse depends on enough attenuation that by the time [4 blocks away] you use Freq 2 again, the other sources are attenuated enough to not be detectable. Adjustments in one block must interact to some extent in the next. But that sounds far less predictable that I think block signaling would have to be.
Any suggestions as to where to go for such?
I'd also love to find the original WeeZ bond patent. I've found several applications that mention using it but thus far no reference citing the original patent by number.
I'm a EE & know the basics, you apply AC of a given frequency to one WeeZ bond, and look for it on the one at the other end of the block. An axle will shunt the rails, and the relay drops. The next block uses a different frequency. [WMATA uses 4 on a given track: 12341234 etc.]
But what keeps Block B from dropping when the wheelset is still in A, or even further away? I assume the reuse depends on enough attenuation that by the time [4 blocks away] you use Freq 2 again, the other sources are attenuated enough to not be detectable. Adjustments in one block must interact to some extent in the next. But that sounds far less predictable that I think block signaling would have to be.
Any suggestions as to where to go for such?
I'd also love to find the original WeeZ bond patent. I've found several applications that mention using it but thus far no reference citing the original patent by number.
