SOUTH SIDE RAIL ROAD DEPOT BUILT: 1868.  TERMINUS UNTIL 4/1869 WHEN LINE EXTENDED TO PATCHOGUE.  RAZED: 1906
2ND DEPOT OPENED: 8/3/1906, AGENCY CLOSED: 9/07/1996.
HI-LEVEL PLATFORMS AND SHELTER INSTALLED: 1999 TO ACCOMMODATE NEWLY-ARRIVED C3 BI-LEVEL CARS
WHICH WERE PLACED IN SERVICE JULY, 1999. (Robert L. Myers 1999 data)
1906 DEPOT RENOVATED: c. 2001    Research: Dave Keller

South Side Rail Road c. 1868

Photos/postcards Archive: Dave Morrison unless as noted

Sayville Station View SW 9/29/1987 
Photo: Edward Hand

Sayville Station View NW 2023

LIRR Sayville Map 1966

 
Montauk Branch - Sayville to Patchogue
Track profile map 1994

Typical uses of detonators include: A warning, caution or stop signal in dense fog, when signals are difficult to see.  A warning of a train stopped on the line ahead by an incident or accident—the train crew are usually responsible for placing the detonators.  A warning of ongoing engineering works ahead.
When a signaler or other railway employee requires to stop approaching trains in an emergency.
To alert crews working on the rails if a silent runaway train or train carriage is approaching.

As with all explosives, detonators can become unstable over time and must, therefore, be replaced regularly.  They are triggered by pressure, rather than impact. This makes them safe during transport, as they normally cannot detonate in a bag or storage container. Source: Wiki

Blueprint of Y cabin in 1917 
Cabin north side of tracks 
Archive: Art Huneke

 
Blueprint of Y cabin after Montauk Hwy. grade elimination project completed and former end of double track reinstated – 1930 Cabin moved to south side of tracks.  Archive: Art Huneke

"Y" Cabin east of Sayville c.1925 Photo: James V. Osborne
Archive: Dave Keller

Y" Cabin east of  Sayville c. 1929 prior to the grade elimination project.  View NW - Archive: Art Huneke Info: Dave Keller 

The double track was reconnected after the project and placed back in service to its original location, and the original cabin was left in situ.  Once the project was completed, the tracks placed back in service and the cabin moved to the south side of the tracks, it was re-manned. 

You’ll notice the temporary structure, which dates to the 1930 project is ALSO wearing the keystone call sign as is the original cabin in the c. 1929 view.  It is my opinion that the original cabin in photo #1 was given this sign sometime after the c. 1925 photo was taken.  It was removed and placed on the temporary cabin and, once the project was completed and the older cabin restored to duty, it was placed back on that structure to identify it.  The cabin was permanently placed out of service and removed on 6/7/1939 and a spring switch installed.  It was protected by “PD” signal #16 controlled from “PD” tower effective that date.  Dave Keller
 

"Y" INTERLOCKING: (R.C.) EAST OF SAYVILLE (BLOCK STATION CONTROLLED FROM “PD.” IN SVC: 06/07/1939. OUT OF SVC: 5/06/2006 WITH CLOSING OF "PD" TOWER.)   Research: Dave Keller

CP (Crossing Predictor) a different signal system being used at Sayville to help manage the length of time the gates are down. It provides consistent warning times for crossings under the conditions of varying train speeds. These were installed at several crossing in the Sayville area in the 90's. 

This simply alerts the engineer to the limits of this system in operation. When they had low platforms, the platform extended right up to the crossing. When you pulled in, if you stopped half way in the station, the gates would come up; when you started from the station, about 3/4 of the way through, you would trip the gate circuit and the gates would come down.  End CP sign 12/31/07 Photo: Mike McDermet

The term controlled point is not used on the LIRR, rather they use remote controlled interlocking, etc. For instance, east of Sayville is a point remotely controlled by PD tower where the 2 tracks merge into one, and that is simply called "Y"