stimac@tymix.UUCP (Michael Stimac) (01/22/86)
Someone asked in passing what the type of signal used by the former
Pennsy is called.
It is called a "position light" signal. This type of signal was
installed about the same time that the original catenary installations
were made. The reason it was chosen was that it was thought to be
less likely to be obscured by the overhead wires and catenary
supports. The original position light signals had four lights
in a row. This was later found to be unnecessary, and the three-light
rows were then employed.
The color of the lens roundels ("lunar white") was chosen for
maximum visibility in the foggy conditions often found in Pennsy
electrified territory.
The position light signals were also felt to have a high degree
of fail-safe protection. No moving mechanical parts, other
than the controlling relays, and if any lamp position goes out,
the signal can still be read.
Position light signals were also employed on the Norfolk and Western
Railroad.
I am interested in RR signalling, and have enjoyed the recent
discussion along that line. Let's hear more about mainline
railroad signalling, in addition to subway signalling.
Michael Stimac
...ucbvax!hplabs!oliveb!tymix!stimacroma@uiucuxc.CSO.UIUC.EDU (01/27/86)
> Okay. My favorite signals were/are on the Chicago and North Western > railroad. They used semaphores (with moving parts, unlike the Pennsy > position signals you describe) with a red, yellow and green lens in > the moving portion. The reason I wrote "were/are" in the above sentence > is that the North Western has replaced their semaphores on the line > going past my parents' house in Milwaukee with your standard "traffic > light" type color signal. But I've continued to see semaphores around > Chicago. I imagine it's only a matter of time before all of them are gone. > > Carl Blesch There are indeed plenty of semaphores on the C&NW in Chicago. Though they ripped out one of the three mains between Clybourn and Canal (in Evanston) on the main line to Milwaukee, I believe they retained the semaphores in the area. But by far the most abundant supply of semaphores I have ever seen is in the approach to the Chicago Passenger Terminal. Sadly, the grand old station was demolished in 1984; however, the semaphores remain. No matter how many times I'm there, I never fail to be impressed. The station itself has 16 tracks. Departing movements from the station pass two dwarf signals which are really semaphores. They consist of white disks with a red stripe through the center, giving the impression of a semaphore blade. This disk is rotated as would a 'real' semaphore to give the appropriate positional and color indication. After passing two such dwarf signals, outbound trains pass two or three regular signal bridges as the throat narrows to eight (or is it six?) tracks. Each track is governed by three-head (!) semaphores. And there are more of the same on each track for inbound movements! Just out of the station, the lead tracks split into two main lines of four tracks each. All this takes place on a curve, but is unfortunately relatively inaccessable because the tracks are elevated at this point. But it's worth checking out. The C&NW's Chicago Terminal is one of my all-time favorite railroad spots -- because of the multiple iron, dozens of semaphores, the neat old 1911-era terminal building with its arched and green-tiled ceiling, and the scores of yellow and green F7's and E8's hauling matching bi-level trains on short headways during rush hour. The terminal building is gone along with the F's and most of the E's and the green- and yellow-painted cars, but the station is still a busy and interesting place. This is where I first remember entering Chicago and I subsequently spent a good portion of my teenage years there watching trains. Needless to say, lots of memories.... As an aside, some roads used notched vs. square semaphore blades to differentiate between block and home signals. C&NW does so by staggering the heads of signals (whether semaphore or other) for block signals and aligns them vertically for home (interlocking) signals. Thus, when a stop indication is encountered, it is a 'Stop and Stay' indication if the red lights are in line with each other or a 'Stop and Proceed' indication if the red lights are out of line. (For interlocking signals requiring only one head, a dummy head consisting of a red signal is posted.) Also, block signals have number plates, while interlocking signals do not. This is fairly standard practice. Jon Roma Computing Services Office, University of Illinois at Urbana-Champaign UUCP: {ihnp4,pur-ee,convex}!uiucdcs!uiucuxc!roma ARPANET: roma%uiucuxc@uiuc.arpa CSNET: roma%uiucuxc@uiuc.csnet