Listing is for one controller board. Buyer specifies whistle/horn button activation (positive DC) or bell button activation (negative DC). This board replaces the shaded pole relay used in various applications by Lionel in postwar trains. It makes and breaks contact on the blue wires with a push of the whistle or bell button. It can switch AC or DC voltages. Please specify if you want relay to activate on positive DC offset (Whistle/Horn button) or on negative DC offset (bell button). Board can be made either way. It can also be used to add any functionality that you need. It will switch any load off and on with the whistle/horn or bell button. If you have a new horn setup with 9v batteries but your relay is erratic, this board will switch it reliably.If you want to add a light that comes on and off with the whistle/horn or bell button, this board can accommodate that. It can activate a small motor or solenoid when the whistle/horn or bell button is pressed in a locomotive, tender, car or layout building.Want to drop a crossing gate when the horn, whistle or bell sounds? Try this board. Can also be used to switch your whistle or horn to be activated by a bell button. Tired of your diesel horns and steam whistles going off at the same time? Switch one to the bell button. This is a new manufactured item. It operates with transformers with a whistle lever or button and with battery operated whistle buttons or can be configured to activate with a bell button. It is polarity sensitive so you may have to reverse track wires for successful operation. Instructions included. Please see my other auctions for:Lionel Diesel Horn relay – Replaces battery and relay in locomotives.Lionel Whistle relay – Operates AC or DC whistles in Lionel tenders. Lionel Teledyne relay – Replaces mechanical relay in Teledyne setups.