MINI-PROTOTYPE SOUND UNIT

Small Scale Railway Co. 's Mini-Prototype Sound Units are small enough for N Scale freight
cars and can be easily installed within locomotives or rolling stock of HO, S, O and G Scales.
All sounds were processed from recordings from the actual prototypes. Power is most
easily provided using a battery, and track power can be use to extend battery life. Instructions
are given describing how rechargeable batteries can be connected and recharged via track power.

The Mini-Prototype Sound Unit uses an optical sensor, mounted through the floor of the loco or
rolling stock, to monitor black and/or white stripes painted on one of the truck axles. While in
motion, the sound unit's microprocessor can synchronize the chuffing sound to the change in
invisible (Infa-Red) light reflected off of the striped axle. The microprocessor also uses this
information to measure speed and deceleration, and automatically activates the various sounds
that are programmed into each sound unit. Maximum chuff rate is 5 to 7 chuffs per second.

Example:
At the first detection of movement, the microprocessor may select a combination of sounds
consisting of bell ringing, safe to proceed whistle or horn, chuffs, and/or drain cock purges.
Once the engine accelerates to a fast enough speed, it will usually choose to give a prototype
whistle pattern. While in motion the steam engine type sound unit will continue to give chuffs,
the diesel will just rev. at a high RPM. By default, a prototype whistle or horn pattern will be
given every 60 to 90 seconds. If the user desires, an optional reed switch (or hall sensor) can
toggle an input that can activate a whistle or horn pattern when a magnet is passed along the
track. This feature will allow prototype whistle or horn patterns to be given at road crossings,
passing trains, switch towers, etc. If the Mini-Prototype Sound Unit equipped train slows at a
reasonable rate, the microprocessor will activate the sounds of squealing brakes. While not
in motion, the sounds of air and/or steam purges will be given with a randomly operating
air pump and running steam generator sound. The sound units are designed for
"hands free operation".

Installation is as follows:

1) drill 1/4" to 1/2" diameter hole through bottom of a box car over an axle
2) paint that axle black with a white stripe
3) install sound unit with double sided foam tape with the speed sensor poking through
the hole at the axle with the black & white stripe
4) glue or tape the speaker to the box car
5) add 9V battery & turn switch ON…ALL DONE

Most sound units contain around 12 different prototype whistle or horn patterns, that last anywhere
from 1 Second to 20 Seconds in duration. Except for the diesel, all sound units can generate
4 or more different types of "chuffs", and many are capable of providing brake squeals. Each
sound unit is different and contains the sounds from the actual prototype. No "fake" sounds are
from a synthesizer, all sounds are from the real engines (except Chuff Only and Micro-Diesel unit).
The sound circuit unit measures 3.7" x 0.6" x 0.8" can fit into 3.7" or longer tender, rolling stock
and dummy engine shells. For larger scales, size is less critical. The sound units can be
purchased with 1 of the following speakers sizes: 1.1", 1.6", 2.0" and 2.5". A "Basic" unit comes
with a standard 9V Battery clip for $80. An Alkaline battery can provide more than 5 hr of sound.
Track power can be used to supplement the battery power source for increased battery life
when non-rechargeable batteries are used to supply power. Instructions are given with all
sound units on how to add rechargeable batteries to the sound units at a later date allowing
the rechargeable batteries to recharge via track voltage.