Electronic smoking units used in trains produced by MTH all work in the same basic manner. Current
is run through a heating element, which in turn "cooks" a mineral or petroleum based oil, producing a
safe, non-toxic smoke. MTH has used three basic smoke unit designs: 1) the Seuthe unit, 2) a
puffing unit and 3) a fan driven unit. We will discuss each of these designs.

The Seuthe smoke unit, used by many train manufacturers, consists of a 1½-inch long pipe with a
heating element mounted vertically in its center. The pipe acts as a reservoir for the smoke fluid. The
heating element is powered from a constant voltage board, usually the same one that provides the
engine lights. Smoke is generated in a stream from the end of the heating element stem. Since the
unit uses a fixed voltage, the smoke volume is also constant. The Seuthe smoke unit is not
repairable. If it fails, it must be replaced. MTH used the Seuthe unit in 1994 and early 1995 with the
first release of the following Premier Steam engines only:

•  Scale Challenger 2 and 3 rail models
•  Scale Ps-4 and USRA Pacific 2 and 3 rail models
•  Scale Y-6b and Y-3 Mallets 2 and 3 rail models
•  Scale 4-8-4 Northern 2 and 3 rail models

With the introduction of the RailKing line of Steam engines, MTH began to offer a smoke unit that
would produce smoke in short "puffs" rather than a continuous stream, as the Seuthe unit released.
A piston tied to the motor and drive train of the engine produces this puffing effect, by forcing air into
and out of the unit across the heating elements. Smoke fluid is brought to the elements by means of
a fiberglass wicking material. The wicking provides for much greater fluid capacity, which translates
to less frequent refills of the unit. Track power is applied to the elements, so the volume of smoke
varies with changes in track voltage. Unfortunately, This type of smoke unit has two distinct
disadvantages. First, airflow only occurs when the engine is in motion, which means prolonged idle
in neutral can cause overheating and damage to the wicking and circuit board. Second, the unit is
very large and does not allow for usage in smaller steam engines, such as the 0-8-0. Because of
these difficulties, only 3 models were equipped with this type of unit: the 1995 Mohawk (NYC and
ATSF), the 1995 Hudson (NYC and UP), and the 1996 Streamline Northern (N&W J and ATSF).

The fan driven smoke unit was introduced in late 1995 in the Premier SD-45 diesel and the Premier
Empire State Express steam engines. The unit is similar to the puffing unit, except the piston
assembly is replaced with a DC powered fan unit. This provides a continuous flow of smoke from the
unit whenever power is applied to the engine. A constant voltage DC circuit on the unit's circuit board
controls the fan motor speed. Additionally, this decreases the size of the unit so that it can be
installed in most steam engines, many Premier diesels, and even contemporary versions of the
Tinplate Traditions steam engines.