Channel letters are the type of signs you often see above large franchises. Letters and graphics formed from aluminum and illuminated with LED's. There are three main styles, face-lit, halo-lit, and non-illuminated. These are further explained below.
Face-Lit Channel Letter are the most common. The LED's are mounted inside the letters facing forward which causes the translucent face to light up. The LED's are typically white but can be other colours. They can even change colour.
Halo-Lit, Back-Lit or Reverse Letters typically have opaque aluminum faces with the LED's inside pointing towards the wall, this creates a "halo" effect around the letter. This is also available with colour LED's and can be combined with face-lit to produce both effects.
Non-Lit Channel Letters are just formed metal letters and logos, painted and mounted to the wall. They have very little visibility at night and are more suitable for businesses with only daylight business hours.
A raceway is an aluminum channel that runs behind the entire set of channel letters. It houses the wiring and the power supply. This method requires that only one wire be fed to the sign through the wall of the building. It also makes it easier to relocate the sign to a new location. More than one raceway may be required depending on the overall shape of the sign.
Flush mounting involves mounting each individual letter and component flush to the wall. A wire has to be fed through the wall behind every letter to a power supply located behind the wall. The benefit of this method is no raceway is visible and the power supply will generally last longer because it is not exposed to the elements. The drawback is that many holes need to be drilled into the wall to accommodate this type of sign.