It really depends on what you want the signal to do.
Here is a link that may be of use to you.
http://www.tinyurl.com/mrr-signals
The following link has two circuits that may be of use. One is called a Block Animator and one called a Signal Animator. These are very simple types.
http://www.logicrailtech.com/index.htm
Elmer.
The above is my opinion, from an active and experienced Model Railroader in N scale and HO since 1961.
(Modeling Freelance, Eastern US, HO scale, in 1962, with NCE DCC for locomotive control and a stand alone LocoNet for block detection and signals.) http://waynes-trains.com/ at home, and N scale at the Club.
I recently acquired a HO scale block signal from BLMA and was wondering a few things: First, BLMA suggest numerous sites that offer signaling circuitry and I was wanting to know what exactly am I looking for and any suggestions on who I should go with and which signaling circuit I should get. Keep in mind I am kind of a newb so user (set-up) friendly would be a plus. Secondly, speaking of set up how hard are they to set up, are the directions easy to understand? If not does anyone have any suggestions? Thanks!