This John Plocher Design, the HO or N scale DCC Flag Man gives the Time Table and Train Order (TT&TO) operator a convenient way to "flag out" and warn other trains that he's occupying HO or N scale main track, it also provides a convenient track power indicator and can be used test DCC track. The Flag Man has contacts that bridge the track (and trigger occupancy circuits) and light an LED "lantern" to warn approaching trains of his presence. The LED Lantern may be optionally placed high or low. The 8-pack part is a revised design by John Plocher and more information may be found here. You will need to solder a resistor and LED to the Flag Man's body and then solder the flag man to his base. The circuit board parts snap apart, since red LEDs can withstand a 30 Volt reverse bias, there is no need for polarity and the LED may be installed in either polarity on either the upper or lower hand. Weights are supplied.
Here's a link to nice video by Miles Hale on how to assemble the flag men
Also available in a 4 pack