RCS and Beltrol controllers and transmitter/receivers can be purchased with accessory ouputs which can be used to operate the soundcard horn or whistle. The wiring diagram for connecting the soundcards to RCS Beltrol is shown below.

The Brian Jones Mac Five uses one channel for loco speed and direction but has no accessory channel. The second channel can drive a separate mechanical servo and microswitch to operate the horn or whistle.

Controllers from Mtronics and Roundhouse are connected in a very similar manner but only the Roundhouse product has outputs for the front and rear lights, They also have no accessory channel and so a separate mechanical servo and microswitch is needed to operate the horn or whistle.

Controllers from Cliff Barker are also similar except that the horn or whistle can be operated by the coupler facility and they have a rear light only which is pre-fitted. They also do not require the capacitor. The pulse rate must be set to 4KHz to work with the soundcard.

The LocoLinc KLR-102 and KLR-106 receivers have accessory terminals which can be used to operate the horn or whistle. They do not require a capacitor.

In all cases, the horn or whistle operates on a momentary basis ie. It sounds when the switch is closed and stops when the switch is opened.