By the 1930s, Britain had built itself a fully switched, long distance, national telephone network. The trunk was the core of long distance lines linking the major cities of Britain. The branches were the feeder lines that came off the network to supply individual exchanges.
The new network made it ever easier for people to call long distance. But phone users needed to be told the new capability was there.
The introduction of Subscriber Trunk Dialling (STD) was confusing for many people. Until then, all long-distance trunk calls were made via the operator. Now STD required callers to dial the full telephone number themselves. It also introduced a brand new price system and people were worried that their bills would go through the roof.
It demanded a great deal of skill and tact from The Post Office's marketing team to get the message across. However, as the telephone exchanges were upgraded gradually, it allowed the message to be spread locally, area by area.
The first launch was in Bristol. The Post Office took out advertisements in newspapers to explain what was happening. Small information kiosks were set up in department stalls, leaflets were handed out explaining the new service and stickers were made with reminders on, for people to put on their telephones.
No matter how much you enjoy the telephone, it can still be a shock when the bill lands on your doorstep.
When time-based charging was introduced it became almost impossible to estimate your bill. Even if you knew the length of your call, The Post Office had 15 separate charge tariffs in place. Which is where the Monitel, an independently supplied telephone accessory, came in.
It sat under the telephone, timing the length of calls and calculating their cost. Programming was by means of a punch-hole card, which stored all the separate charge tariffs. At the end of the call you could push a button and it would show how long the call was and how much it cost, on a digital display. This was brilliant for a small business that needed to keep a close tab on costs, and saved many flatmates falling-out over who had to pay how much!
The introduction of subscriber-dialled calls needed an entirely different pricing mechanism. Call prices were measured using two metrics - time and distance - and the cost of a call was worked out by multiplying the length of the call with the price band for the distance called. No longer were trunk calls charged only in 3-minute blocks, and now local calls too were timed.
There were four different call radii. Local wasn't a fixed radius, but was defined by arbitrary groups of exchanges. For the most part, though, local calls were up to around 15 miles. The three trunk call tariffs were measured between the area's 'Group Switching Centres': up to thirty-five miles; thirty-five to fifty miles; over fifty miles. International calls still had to be made via the operator.
Customers' quarterly telephone bills didn't include cost breakdowns then, so The Post Office developed very elaborate metering systems to ensure accuracy, with photgraphic records that could also be referred to in case of any dispute.
Visit our interactive demonstration and try it for yourself. A new window will open.
There's still an air of mystery about this early payphone, as as it is not entirely clear where it was used.
It was made in the late-1880s, a few years after the first payphone had been introduced, but was more advanced because it provided full usage for the public, subscribers and trunk subscribers alike.
The slots on the top accepted coins from the general public, and the slots on the front accepted the passkeys of subscribers, who paid an annual fee in advance for unlimited calls. Subscribers received unlimited local calls but had to pay for trunk calls. 'Trunk subscribers' also received unlimited calls to the trunk, but like everyone, public and subscribers alike, they also paid for the actual call by dropping coins in the top.
Most payphones were installed in staffed locations, such as a public telephone centre, but the complexity of this one meant that it could be left unattended. Most likely it was in a hotel, railway station or department store, but no one knows for sure.
By 1897 connecting up telephones underground between short distances was a fairly straightforward process, but linking greater distances presented much greater problems. For one thing, the copper conductors needed to be very much thicker. This section of cable showed it could be done and comes from the world's first subterranean, long-distance trunk connection between London and Birmingham.
The cable carried 38 pairs of wires - the pairs provided one wire to send signals along and another to return. Each wire was wrapped in paper to insulate it, then they were bunched and wrapped in paper again and finally the whole package was surrounded by a lead sheath.
It was 9cm in diameter and each wire weighed 150lbs/mile. This meant the cable was very heavy, but it was safer and needed less maintenance.
In the early days of phones, subscribers could make unlimited phone calls to local numbers for an annual fee.
'Call offices' - payphone kiosks with an attendant who collected call fees - were provided from the 1880s onwards. Anyone could use them and telephone subscribers could show their 'pass key' (a kind of membership card) which let them make local calls without further charge and reduced the cost of trunk calls.
