It the signal is superimposed on the track voltage, it uses the voltage as the carrier for the signal. Digital means it is a series of on-off type signals, which can then filter out any noise. DCC is the first hobby wide system, developed under the auspices of the NMRA, and everyone is jumping on the bandwagon to make the installation easy. Decal - Shortened form of the French decalomania , which literally means to transfer a pattern or design by applying pressure. Despite this derivation, a decal uses water, not pressure, to achieve a transfer.
Decal paper is essentially paper coated with varnish.
The decal can be floated onto any surface, such as a model freight car, and positioned as desired. Several applications of a decal setting solution are then brushed on, to partially dissolve the film, softening it and allowing it to snuggle into the tiny crevices of a three-dimensional surface. Decals have been standard in the hobby for over half a century, but up until recently, they were made by a printing process. In order to be economical, the cost of setup for regular printing has to be distributed among a large run. Recently some photocopiers can print on the glossy, non-porus surface of the decal.