The rapid expansion of the telephone network in the late 19th and early 20th centuries led to a booming workforce of ‘hello girls’, who connected calls at central telephone exchanges.
But the introduction of automatic telephone exchangesallowed callers to dial numbers themselves, leading to the disappearance of one of Britain’s first female workforces.
How didthis technology work, and how has it shaped the way we communicate today?
What is a telephone exchange?
In 1876, Alexander Graham Bell had patented his telephone, allowing conversations to be held over long distances. The technology took off and telephone networks expanded rapidly—butthey could not offer dedicated lines between one user and any other.
Instead, the heart of the network was the exchange, or switchboard, where operators manually routed incoming calls to their destinations.
How does a telephone switchboard work?
Telephone users would pick up the phone, connecting immediately to the switchboard. “Number, please?”, the operator would ask, and then “Hold the line please” as she expertly removed and inserted jack plugs to connect the call.
If the number was on the operator’s switchboard, they would connect the call by plugging the ringingcable into the relevant jack. If not, they would transfer the call to the correctexchange, where another operator would be able to connect the caller.
Who were the ‘Hello Girls’?
The job of a switchboard operator took concentration, good interpersonal skills and quick hands.
The Post Office, which ran the telephone service in the UK, soon realised that women and girls were much more skilled and reliable than the messenger boys who had first taken on the job.
Science Museum Group collection
As the network expanded, suddenly there was a new employment opportunity for women: one that gave them some economic independence and an identity outside the home.
Hundreds of operators worked on each switchboard in towns and cities, and the service was efficient and largely confidential.
In smaller neighbourhoods, the switchboard might be operated by a single individual. The village postmistress’s ability to listen in on private conversations (strictly forbidden but difficult to prevent)soon taught phone users to be careful what they said.
How did the technology develop—and why did it need to?
Science Museum Group collection
The rapid increase in demand for telephones and reliable connections posed a problem for the telephone companies. More lines meant more switchboard operators—an expensethey were keen to control.
And fast as they worked, operators could be overwhelmed by the volume of calls at busy times, leaving callers queuing for a line.
Many inventors began to put their minds to automatic methods of handling switching, so that customers could dial each other directly.
The most successful was not a telephone industry professional, but a funeral director: Almon B Strowger of Kansas City, USA. Strowger apparently suspected that a telephone operator was diverting requests for his services to a rival firm of undertakers.
He set out to establish what he called the ‘girl-less, cuss-less telephone’, using machinery to automate the process of connecting telephone callers.
How did automatic dialling work?
Almon Strowger's design of 1889, widely adopted in its developed form in both Britain and the USA, became known as ‘step-by-step’. The name derived from the wayselectors ‘stepped up’ from one line to another until they successfully found a route through the exchange.
The key component of the system was a telephone with a rotary dial. Just like a modern keypad, the dial had 10 positions numbered from 1 to 0. The caller would place a finger in the hole over the number required, and rotate the dial to its stopping point.
As the dial rotated back to its starting position, it sent electrical signals down the line. This controlled the stepping of the selectors.
The first automatic telephone exchange in the UK
The Post Office opened the first automatic exchange on the public network at Epsom in Surrey in May 1912. This was the same year it had obtained a near-monopoly on the provision of the country’s telephone service.
It took decades for automatic dialling to roll out across the country. Installing an automatic exchange was expensive, and while savings were made by making operators redundant, it took time for this to generate cash. The two world wars also had a depressing effect on investment.
One of the last manual switchboards in the UK—and the last to run in London—was at Enfield, north London. It switched to automatic connection at 13.30 on Wednesday 5 October 1960.
In the early days of automation, there were no area codes. In order to automate large cities such as London, the GPO introduced three-letter exchange codes (such as WIM for Wimbledon) at the beginning of each seven-digit number.
Special selector equipment ‘directed’ each call to the desired exchange and number.
How did the system go digital?
The Strowger system and its successors were all electromechanical devices, involving physical moving parts. In 1937 the British telephone engineer Alec Reeves proposed pulse code modulation (PCM), the basis of digital electronics, as a means of switching calls.
His idea took off in the 1940s with the development of the transistor, which made it possible to build smaller and lighter electronic devices. In September 1968, the Post Office opened the world’s first all-digital PCM telephone exchange, Empress, in west London.
What is the legacy of these breakthroughs today?
Telephone systems worldwide have since adopted digital technology. The now-familiar keypad has replaced the rotary dial, as exchanges no longer need sequential electrical pulses to drive machinery.
The London region’s last manual exchange, at Upminster in Essex, finally converted in 1970. The last manual exchange in mainland UK, at Abingdon, closed in 1975.
Like computers and other modern digital technologies, today’s electronic exchanges occupy far less space and have many times the capacity of the earlier manual exchanges. But the operator is not entirely extinct.If you’re having trouble making a call, you can still dial 100 and ask a human being for help.
- Life on the exchange: Stories from the Hello Girls (Science Museum blog)
- Long before Siri, there was Emma Nutt (Smithsonian)
- A rare look inside a telephone exchange (Ars Technica)
