[PRCo] Re: MetroRail Signalling

[Schneider Fred]

I'm also out of my element but Russ's explanation is that the they  
are audio frequency but you could only hear them if amplified.

But that they are in the thousands of hertz per second instead of  
hundreds.   And at that frequency they do not need insulated joints  
except when the block length is very short as it would be in  
interlockings.

Of course that is a misnomer because the entire railroad is  
interlocked so you cannot screw up ... what we are saying is where  
the block is very short due to crossovers, switches or turnouts, at  
junctions.   Then you would need insulated joints.


On Jun 30, 2009, at 12:46 PM, Joshua Dunfield wrote:

> 2009/6/29 Schneider Fred <fwschneider at comcast.net>:
>> Russ Jackson called me this evening ... I finally had an opportunity
>> to ask him to explain the Washington Metro signal / ATO / ATC system.
>>
>> His answer is simple.   It is fundamentally no different from the old
>> Pennsylvania Railroad signals that I understood except that it uses a
>> signal frequency in the audible range ... if amplified you would be
>> able to hear it ... the frequency is in the 1000s of cycles per
>> second instead of in the 100s of cycles per second.
>
> I'm out of my depth here, but frequencies in the 100s of Hz are well
> within audible range; a tuning fork produces 440 Hz, and the lowest
> note on a piano is about 25 Hz, IIRC.  So that part of the explanation
> doesn't seem quite right.
>
> Digressingly,
> -j.
>
>