Type D trackside signals

The lights in each signal head are arranged in a vertical line.
Each light is a different color.

 Type G trackside signals

The lights of each signal head are arranged in a triangle on a circular 'target.'
Each light is a different color.
These are sometimes referred to as 'tri-light' signal heads.

 Type SA searchlight signals

Each head of a searchlight signal has a single lamp in the center of a round 'target.'
In the full-size signals a movable filter inside the head changes the signal color.
Today's scale models of searchlight signals use tiny LEDs to produce the green, yellow and red colors.

 Ground level dwarf signals

Dwarf signals are low-height signals mainly used at stations and rail yards.
A 2-color dwarf signal often is used to indicate the position of a turnout.
They take on quite a variety of forms -- vertical, position light or searchlight.

Block signals in other scales  >>>  O scale   S scale  HO scale