Hi gang,
I just picked up John Signors latest book "The Los Angles Division" and in it he talks about simi automatic block signals that were used inside the LA terminal limits (Between Taylor jct. and Alhambra?). The signals had "S A" plates on them.
So, How does a simi automatic signal work?
He called it semi-automatic, didn't he?
"SA" signals weren't just in LA. On SP, an "SA" plate on the signal means it's the last human-controlled signal you pass as you're leaving an interlocking (or maybe CTC) and entering automatic-block territory.
So it's semi-automatic, but probably all the other interlocking signals are semi-automatic too -- if the operator throws the lever to clear a signal, it won't clear if a train is sitting just past it.
The Simi Automatic Signals would be the ones in Simi Valley.
On PRR, a semi-automatic signal was a block signal controlled by an operator. However, operation of such could be established whereby it functioned as an automatic signal and did not have to be manually cleared by the operator after each movement. Such signals often protected power or electrically locked switches, and were at locations where conflicting movements were infrequent, hence it was more expedient to have a provision for the signal to automatically clear for following movements on the primary route.
Erik_Mag The Simi Automatic Signals would be the ones in Simi Valley.
Thanks for the replies. Good info
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