4 light signal redgreen 2yellow T junction square head This 4 aspect signal is placed at the side of the track mainly at diverging routes It is suitable for any layout based from around 1970 when this style of signal head came into use & examples could still be found on the network until 2009 when the new slimmer signals became standard although this replacement programme began around 2000 A red light indicates stop a double yellow light indicates caution the next signal is yellow & at caution a single yellow light indicates caution the next light is red & Green indicates permission to proceed or route clear This signal is ready to use out of the box & features a prewired resistor to allow the safe operation of the signal from a 12 Volt DC power supply