You can find MTH diagram here: http://www.mthtrains.com/content/30-11005
You will need either a relay, isolated track section or the items shown in these notes
o Block Signal (Single Track) (Double Track) diagram
+ This type of signal is normally green signal. When a train enters the isolated rail section the signal turns red signal. When the train leaves the isolated rail section the signal turns yellow signal, and then after a short time, returns to green signal. Since this type of signal has 3 wires it is more complicated to wire and also requires a 12v DC Relay (Radio Shack 275-206c or equivalent), $6.49; and a Full Wave Bridge Rectifier (Radio Shack 276-1173), $1.99. The polarity of the full wave bridge rectifier is not important. Follow the diagrams to wire this type of signal.
Or by use of TAD and Connector as shown on MTH Site
Mort
(downloaded from other posts on wiring signals)