An acoustic coupler sends and receives computer data over a telephone line using sounds. They were used in the early days of the internet and are still used in countries with less advanced telecommunications networks and by deaf people. They were used when it was impossible to use a standard modem plugged into a telephone wall socket. Today, they are useful when visiting countries with wired phones and no cellular network. They are also still used in devices for deaf people.
An acoustic coupler is a device that sends and receives computer data over a telephone line using sounds rather than electrical signals. The devices were popular in the early days of Internet use, when traditional modems weren’t always practical. Today they are mostly seen in countries with less advanced telecommunications networks and in equipment used by deaf people to make telephone calls.
It used to be that in many places it was impossible to use a standard modem plugged into a telephone wall socket. This could sometimes be a physical problem where the phone wires went straight into the wall meaning there was no outlet. In other cases, there were laws prohibiting anyone from plugging electrical equipment directly into the telephone system.
The solution for those who wanted to connect to the Internet was the acoustic coupler. The most common type was a device that you placed your phone handset on top of. There were usually padded seals so that no noise could enter or leave the mouthpiece and earpiece.
The device then transmitted and received tones which computers at each end could translate into data. You can get an idea of how that works when you push buttons on a phone today and each digit makes a slightly different noise. Even if you’re not old enough to remember them, you may have seen an acoustic coupler in movies like WarGames or Ferris Bueller’s Day Off where Matthew Broderick’s characters used them to access computers over the telephone network.
Today, few computer users in developed countries need an acoustic coupler. However, they can be useful when visiting countries where some phones are still wired and where there is no cellular network to enable mobile broadband use. Some travelers even use them to connect to the Internet through payphones. Since even today’s fastest acoustic couplers are only about half as fast as a standard dial-up connection, this technique is far from ideal, but it may be passable for less data-intensive tasks like checking e-mail.
Acoustic couplers are also still used in some devices used by deaf people, known by terms such as minicom or teletype. Each user types a message which is then converted into sound, sent via laptops and then converted back into text which appears on a screen at the other end of the device. In some cases, the deaf person is connected to an operator who has a device and then transmits messages to and from a fully hearing caller on a normal telephone.
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