The sound card is designed for use on track powered railways where the DC voltage varies from zero to a maximum voltage of between 7.2 and 30 volts. Controllers can be pulse width modulated or linear. It is suitable for use on some DCC systems where it can be connected across the motor.
Note that the horn/whistle is shown as a negative (ground) input connected to terminal H1. A positive horn/whistle input should be connected to terminal H2.
The battery pack shown provides power for the diesel engine tickover and the steam hiss when the track power is switched off and the loco is therefore static. Any small battery pack can be used, from 7.2 to 9.6 volts.
Without a battery pack, the sound card will switch itself off in track powered locos at very low speeds as the locomotive comes to a halt.
The horn/whistle can be operated by means of a switch or pushbutton mounted on the loco, by means of a reed switch operated by trackside magnets or by modifying a wireless actuator for a door chime or garage door.
When used with trackpower, the horn/whistle will start the first time the switch is closed and stop the next time the switch is closed. Therefore the horn/whistle starts at the first magnet and stops at the second when trackside magnets are used.
The quality of the sound depends on the smoothness of the DC track power. Some popular brands of controller, like LGB, produce a very rough DC voltage which will lead to inferior sound reproduction. The solution is to purchase a 2000 micro farad, 25 to 50 volt, polarised capacitor from your local consumer electronics store. Remove the soundcard jumpers and solder the capacitor across the jumper pins as shown below. This will ensure that the roughest controller will produce a sound quality equal to that of a battery powered locomotive.
