Button A and Button B prepayment telephone equipment, 1940, 1950 public telephone
A new type of coin-box was introduced, the well-known Button A and Button B prepayment equipment, and for over 25 years its design remained unchanged despite various developments in the design of kiosks. It was usually installed in both automatic and central battery manual exchange areas. To make a call in automatic areas, users inserted the appropriate fee which prepared the circuit for dialling. In manual areas, callers were connected to the operator on insertion of the call fee and, in both cases, the caller then depressed Button A. This allowed the coins to be deposited into the cash box and the call to be transmitted. If a call could not be connected for some reason, or if there was no reply, Button B was depressed, the line was disconnected for five to seven seconds and all the coins were returned to the caller. Although 6d (2p) and 1/- (5p) slots were available for other calls, the minimum fee necessary to make a local call at the time was 2d. The mechanism was originally designed to check the presence of two pennies by a weighing operation. It was set to a minimum and maximum acceptable weight for the coins as a safety margin, but as the fee was gradually increased to 3d and then 4d the safety margin became smaller and eventually unacceptable. A mechanical counter was considered too expensive as the modifications needed would have been too many and too complex. To overcome this problem a new mechanism was devised by Hall Telephone Accessories Ltd and was in effect a combination of the two basic methods: three pennies were checked by weight and the mechanism waited for the insertion of the fourth penny before allowing the call. The system required the smallest amount of additional equipment and could be easily fitted. A limitation was that it could not be easily adapted for an increase beyond 4d. In 1959 the first versions of the new Pay-on-Answer payphones were being introduced and at the end of the 1950s began to supersede the 'Button A and B' models.
Size: 2736px × 3648px
Location: Great Britain, UK
Photo credit: © Tony Smith / Alamy / Afripics
License: Licensed
Model Released: No
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