Some time ago I distributed an article on signal aspects and general signaling. It was also published in a condensed form in the OERM Gazette. I  believe I have noted some misunderstanding of the meaning of Home and Distant and hope this brief explanation will help. If you find you are still or become confused, read the Southern Pacific or Santa Fe signalman's training material on our web site. If that still leaves you with questions send them to me by e-mail and I will try to answer them or write a additional article based on them if there are several questions on the same topic. Do not limit yourself to this particular subject as I need to write other articles anyway.

HOME SIGNAL 
A 'Home' signal indicates the occupancy of the block immediately beyond the signal. It is equivalent to the yellow and red aspects of a light signal. In the days of two aspect semaphores it was the top semaphore blade that regulated entrance into the block.

DISTANT SIGNAL
A "Distant' signal normally indicates the occupancy of the second block ahead - the block beyond the Home block in the direction the train is going. If that block is occupied it will display yellow.  When the SP and other railroads could only buy two aspect (semaphore) signals, the concept of a Home signal head (blade) for the near block and a Distant signal head for the next block ahead was conceived. The home blade was at the top of the pole and the distant blade was below.

THREE ASPECT SIGNALS
With the introduction of three aspect signals, both semaphore and light, the extra head was eliminated and replaced with the new three aspect signal. If you will refer to your copy of "All About Signals" or the Santa Fe or Southern Pacific signal training courses this will become clear.

The relay controlling a three aspect signal became a [signal number]HDR (Home Distant relay) and a relay rePeating these aspects became a [signal number]HDPR or HDP. If separate relays control the aspects of a signal, the relay selecting between green and yellow is a [signal number]DR and the relay selecting between yellow and red is the [signal number]HR. For example: 1951HR with 1951 being the signal number.

DIVERGING SIGNALS
On our railroad and most and others using route signaling, a diverging aspect uses two heads. The upper head indicates the condition of the track in the normal direction on the main line and the lower head indicates the condition on the diverging route.

Reference to the aspects shown in the Altamont railfans' California Timetable will show many more aspects that probably will only serve to confuse the subject. For instance they show many aspects that more completely define the track conditions ahead, the speed that the train is to go, or optional or existing aspects the railroad does not want to change. One instance of this is the approach medium aspect. This is either a single flashing yellow signal or a yellow over yellow (and others), allowing a train to go faster than a single yellow (approach) signal, but slower than a green signal. The signal system becomes four aspect instead of the basic three aspect system. We at OERM use only the basic aspects of route signaling. BNSF and Amtrak use a more complex version. The Union Pacific uses a form of speed signaling that tells the engineer almost exactly what speed to run his train (again see the railfan timetable).


SIGNALING AT OIL JUNCTION
Oil Junction is the next planned expansion of the OERM signal system. When the signal bridge and associated signals and circuits are complete and the Interurban Loop is complete, Oil Junction will be not only a pair of intermediate signals on the main line, but a simple form of interlocking.

A southbound train on the main line will see the Oil Junction southbound signal as an approach signal to Middleton. If Middleton is respectively green, yellow, flashing red or red on either the main line or on the diverging route onto the Barn Four Lead, the southbound Oil Junction signal will display green, green, yellow or yellow respectively. If the track between Oil Junction and Middleton is occupied with a northbound train the signal will be red. If it is occupied with a southbound train the signal will be flashing red. For a northbound train the aspects will be similar once the signals are installed at Leola, until then the maximum aspect northbound will be yellow.

A train or interurban car proceeding northbound on the planned Interurban loop. will approach a red signal. If the mainline is clear or if it is clear one direction and a train is proceeding away in the other, the northbound home signal on the Loop will automatically clear to the appropriate aspect to allow the train on the Loop to proceed through the spring switch northward on the main line. If  a train proceeds just past the southbound signal and waits the prescribed time, the southbound signal will clear allowing the train or car to proceed south.  A southbound train desiring to enter the Loop will stop at the southbound signal and push a button on a pole. The switch can then be aligned for the Loop and the signal will display a proceed aspect for the Loop. Eventually I hope to use a switch machine to operate the switch. In the event that it is desired to make  Middleton Siding a second main line, operation will be similar to that for the Interurban Loop. The circuits for most of this are already wired and only need to be activated.

My general plan is to complete Oil Junction with pushbutton clearing of trains onto the main line from Middleton Siding and the Pie Yard. When the Interurban Loop is built, the circuits will be reconnect to the Interurban Loop. The next signals I hope to install are to be North Leola, followed by inserting the signals at South Leola complete with leave siding signal. North Leola circuit design is complete and South Leola is about 80% complete.

As a point of interest, both crossing and wayside signal circuits for Fourth St. and Seventh St. are complete and waiting for construction of our track to Perris. Double heads for diverging routes, will be used for southbound  moves at Oil Junction. This will be a case with a pole on the present distant semaphore foundation. Double heads for diverging routes will also be used northbound at South Leola and southbound at North Leola.

Gene Cranston