How to Build a Small Telegraph


A telegraph works by basic principles of electricity and electromagnetism. When the telegraph key completes an electrical circuit, it energizes an electromagnet that pulls a sounder toward it, making an audible click. A telegraph can send messages over long distances, and it can also be made in very compact size. It is possible to construct a telegraph on one portable wooden board. It would not be very useful for actual communication, but it can demonstrate how a telegraph works.

Things You'll Need

  • Wooden board to hold all telegraph components
  • Six-inch iron nail
  • Small block of wood, six inches high
  • Six-foot length of insulated copper wire
  • Two 1/2 inch wood screws
  • Wire strippers
  • D battery

Make The Sounder

  • Strip the insulation from both ends of the copper wire.

  • Wrap the six-foot length copper wire around the nail about 100 times. Start wrapping at one end of the nail and wrap only in one direction around the nail in overlapping coils. Leave about six inches of free wire extending from each end of the nail.

  • Drive the nail into one end of the wooden board. Drive the nail only far enough to hold the nail steady.

  • Nail the block of wood into the board directly adjacent to the first nail. The wooden block should be only slightly higher than the nail.

  • Nail the thin metal strip to the top of the wooden block so that it extends above the nail head. Bend the metal strip so that it rests directly above the nail head.

Make The Key

  • Strip the insulation from about one inch of a six-inch strand of copper wire.

  • Loop the uninsulated wire end around a screw and screw it into the end of the wooden board opposite the sounder.

  • Screw the other strip of metal to the wooden board so that one end of the strip just touches the first screw. Connect the lower wire from the sounder nail to the screw by looping the uninsulated end around the screw head before tightening the screw completely.

  • Bend the metal strip up so that it does not touch the first screw.

Connect A Battery

  • Attach a D-size battery to the board. You can use tape or a store-bought battery holder.

  • Attach the upper wire from the sounder nail to the positive side of the battery. Use tape or attach the wire to the battery holder terminal, if applicable.

  • Connect the wire from the other screw to the negative end of the battery.

Operate And Adjust The Telegraph

  • Press the telegraph key (the bent up metal strip attached directly to the wooden board) down so that it touches the screw.

  • Adjust the sounder by bending its metal strip to position the strip closer to the nail, if necessary. If the strip is too far away, the nail's electromagnetism might not draw the metal down. If it is too close, the strip might not make an audible sound when it contacts the nail.

  • Add more batteries to the board to make a stronger electromagnet, which will exhibit a more powerful pull on the sounder.


  • Photo Credit Hemera Technologies/ Images
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