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Horn Relay Board

£25.80£30.00 inc VAT

These relay boards are designed to control 3 or 4 relays from one of our hand throttles. It has a number of “break points” on the circuit board that gives it a lot of flexibility to be used with [e.g. sound] systems that require isolated switch inputs.

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Model locos often need to operate twin horns and lighting from the hand control box. This used to require a 12 way cable and an expensive connector. It also meant running lighting or horn currents through to the hand control box which requires thicker cables. This relay board solves all of these problems. It enables you to control twin horns and lighting with only two control wires. Note: if you are using this relay board to operate standard car horns it is important to fit the included catching diodes to prevent high voltage spikes damaging your controller.

It measures approximately 76mm x 60mm. Two relays can operate twin horns via one control wire, operating from a centre-off switch. Earthing the control wire operates one relay/horn, connecting to battery positive operates the second relay/horn.

Horn relay board layout

The relay board will greatly simplify the wiring of most model locos. A 6 way IDC connector takes the two spare wires from the 8 core control cable, and screw terminals are provided for the horn and lighting wiring.

The board is manufactured with a number of “break points” that allow the relays to be isolated for use in many applications.

The lighting relay is a single wire operation, but there is space for a fourth relay so that another twin relay system can be implemented. Alternatively the four relays could be worked independently (requiring four control wires).

  • One wire operates twin horns (High for horn 1, Low for Horn 2)
  • One wire operates lights.
  • Relay continuous current handling: 10 amps at 24 volts.
  • Versions available with 3 and 4 relays [4th relay usually used for reversing lights].
  • Versions available for 12 and 24 volt systems.
  • The 24v version can be used with 12v horns/lighting by cutting a single track
  • Wiring diagrams for mixed voltages and the 4 relay version are in our knowledgebase
  • The full circuit diagram is in the manual


The manual is available in PDF format:

Adobe_PDF_file_icon_32x32   Read manual

The manual is designed to be printed double-sided in A4 booklet format. To print the booklet from the PDF on a double-sided printer, select Booklet in the Page Size & Handling section of the print window, and set Orientation to Portrait.