Telegraph
Make information travel faster than people.
Everything for this step
- Field guide
- The electromagnetic spectrum → 2 sections Computer science → 6 sections Electronics and computer hardware → 19 sections
- Builds
- None yet.
- Reference sheets
- 1 sheet in The electromagnetic spectrum
- Sciences it rests on
- Physics
Why this matters
For all of history before this, a message moved at the speed of a horse or a ship. The telegraph breaks that, and the consequences are enormous: coordinated railways, functioning markets, distributed government, weather warning, and a genuinely shared present tense across a whole territory.
The shape of it
- Build reliable batteries first. A Daniell cell — copper and zinc in their own sulphate solutions, separated by a porous barrier — gives a steady output for hours and is entirely makeable at tier 3.
- Draw copper wire in quantity. See wire drawing; this is the physical bottleneck.
- Insulate seriously. Wet insulation is the commonest failure. Glass or ceramic insulators on poles, and gutta-percha or rubber for anything buried or submerged.
- Build the sounder and key: an electromagnet that clicks an armature. Simple, robust, and repairable in the field with hand tools.
- Use a code with variable-length symbols — short codes for common letters. Morse is a good design and there is no reason to invent another.
- Run it along the railway. The right-of-way already exists, it is patrolled, and the railway needs the telegraph for signalling. They pay for each other.
- Add repeaters every so many kilometres, since signal attenuates with distance.
- Then think about what it does to society. Instant communication concentrates power at whoever controls the wire. Decide early whether it is a common carrier or a private asset — that choice shapes everything downstream, including who gets to know things first.
Doing it, step by step
The summary above says what has to happen. This says how, with the numbers that decide whether it works.
1 · Build steady batteries first
A Daniell cell: copper plate in copper sulphate solution, zinc plate in zinc sulphate solution, the two liquids separated by an unglazed porous clay pot. It gives about 1.1 volts per cell, steady for hours — far steadier than a simple acid cell, which polarises and fades.
Connect cells in series for voltage. Maintain them: keep copper sulphate crystals in the copper side so it stays saturated, and draw off zinc sulphate as it strengthens. Needs acids and copper.
2 · Draw copper wire in quantity
This is the physical bottleneck. Pull copper rod through a draw plate of hardened steel with a series of tapered holes, each slightly smaller than the last, reducing the area by roughly 10–20% per pass. Lubricate each pass.
Copper work-hardens and eventually snaps: anneal it — heat to a dull red and quench or cool — every few passes. Measure the diameter along each coil; thin spots are the breaks and high-resistance points of the future line. See wire drawing.
3 · Build the line on insulators, and earth it well
Wet insulation is the commonest failure: bare wire on wooden poles leaks to earth in every rain.
- Poles at regular spacing, tall enough to clear traffic and animals.
- Glass or glazed ceramic insulators with a drip skirt, so a dry path remains under rain.
- Gutta-percha or rubber covering for anything buried or submerged.
- One wire with an earth return: bury large metal plates in permanently damp ground at each end, since the earth carries the return current.
4 · Build a key, a sounder and relays
The key closes the circuit; the sounder is an electromagnet that pulls an iron armature down with an audible click when current flows, and a spring returns it. Simple, robust, and repairable in the field with hand tools.
Signal weakens with distance as wire resistance and leakage grow. A relay — a sensitive electromagnet whose armature closes a fresh local battery circuit — repeats the signal at full strength. Place relays at stations along the line spaced by what the wire and insulation can carry.
5 · Use Morse, and train operators to a speed
Use a code with short symbols for common letters; Morse is a good design and there is no reason to invent another.
The timing is the code: a dot is 1 unit, a dash 3 units, the gap within a letter 1 unit, between letters 3 units, between words 7 units. Train operators on printed tables and test them sending and receiving plain text at a set speed. Every message is numbered, timed and acknowledged by the receiving operator.
6 · Run it along the railway, and protect it from lightning
The railway right-of-way already exists, is patrolled, and needs the telegraph for block signalling — see rail. They pay for each other.
Lightning strikes long wires. Fit lightning arresters — a spark gap to earth — at every station and instrument, and earth them well. Operators do not touch the line during a thunderstorm.
7 · Decide who controls the wire, before anyone does
Instant communication concentrates power at whoever controls the wire. Decide early, in published law:
- Common carrier or private asset — whether the network must carry any paying message on equal terms.
- Privacy of messages — operators forbidden to disclose content, with penalties.
- Priority rules — which messages go first: safety and railway signalling, then public health warnings, then the rest.
That choice shapes everything downstream, including who gets to know things first.