ROTARY Watch the rotary film ↗
A field guide to the local loop

Your finger makes a route.
The network makes it ring.

Follow one ordinary call through the copper pair: dialling a number, counting pulses, finding the other line, carrying voices, and opening the circuit again.

Three-dimensional ivory rotary telephone with a large circular dial
Interactive cutaway
01LIVE DIAL

Give the wheel a number.

Click the finger holes to feel the old rhythm: each digit pulls the wheel back, then releases a counted train of pulses onto the line.

NUMBER BEING SENT — — — Choose up to three digits
Handset lifted · line ready

click a hole to dial · send follows the route below

LIVE DIAGRAMCaller’s phone
LOOP CLOSED
Rotary telephone connected to a telephone exchange and recipient The highlighted signal path changes as the call moves through dialing, switching, ringing, talking, and hang-up. CALLER EXCHANGE RECIPIENT A steady loop carries the call
TIP / RING PAIRtwo copper wires, one complete circuit
01THE DIAL

The dial stores a number.

Lift the handset and the hook switch closes the local loop. Your finger pulls the dial around; the wheel returns one notch at a time, ready to turn a digit into electrical timing.

WHAT CHANGESMechanical movement becomes timed openings in the circuit.

←→ step through the call · space play / pause

Cutaway renders

The route has a physical shape.

Three close looks at the machines behind the six-step journey: the wheel that makes pulses, the selectors that make a path, and the bells waiting at the far end.

Detailed ivory rotary telephone with its finger wheel in a warm studio light 01 / 03 DIAL + PULSES

The dial is a clockwork sender

The finger wheel stores a digit as it turns. On the return, a governor spaces out the make / break pulses that the exchange can count.

Detailed electromechanical telephone exchange rack with selectors and copper wire bundles 02 / 03 SELECTOR BANK

Selectors turn digits into a path

Each counted digit advances a selector or relay stage. Together, those stages connect the caller’s pair to one outgoing pair among many.

Detailed ivory rotary telephone with its handset lifted and amber ringing waves 03 / 03 RING + VOICE

The far end gets an invitation

A separate alternating-current signal drives the bell. When someone lifts the handset, the ringer drops out and the speech circuit takes over.

Visual reconstructions, not a single exact exchange design. Hardware changed by country, era, and manufacturer.

Route decoder

A number is an address, not a name.

The exchange never needs to know who you mean. It reads each digit in order, narrows the search, and ends on the subscriber pair assigned to that address.

This is a simplified local example. Real numbering plans and switching layouts varied, but the idea stayed the same: digits advance stages until one line remains.

Dialled address212
2Central officefirst pulse group
1Apartment blocksecond pulse group
2Line 2 · ringsfinal selector
The last digit lands on subscriber pair 2.
Three things to listen for

It is all timing,
current, and distance.

01

The loop is the path

The two wires form a circuit between the telephone and the exchange. Lifting the handset tells the exchange that the line is ready.

02

Silence can be a signal

Dial pulses are brief openings in the loop. The exchange counts the gaps, then uses the resulting digits to select an outgoing path.

03

Hanging up resets it

Replace the handset and the loop opens. The exchange releases the connection, stops ringing, and makes both lines available again.