What is a Touch Tone Phone?
A touch tone phone, also known as a multi-frequency (MF) telephone, is a type of telephone that uses a keypad to input digits. Unlike the older pulse dialing system, which sent a series of on-off tones, touch tone phones use a combination of different frequencies to represent each digit. This technology has become the standard for most telephones worldwide.
How Does a Touch Tone Phone Work?
When you press a digit on a touch tone phone, the keypad sends a combination of two different frequencies to represent that digit. For example, the number 1 is represented by a 941 Hz tone followed by a 1336 Hz tone, while the number 2 is represented by a 697 Hz tone followed by a 1209 Hz tone. This process is repeated for each digit, and the combination of tones is what the phone’s central office uses to identify the number being dialed.
Here’s a table showing the frequency combinations for each digit:
| Digit | First Tone (Hz) | Second Tone (Hz) |
|---|---|---|
| 0 | 850 | 1336 |
| 1 | 941 | 1336 |
| 2 | 697 | 1209 |
| 3 | 697 | 1336 |
| 4 | 703 | 1209 |
| 5 | 703 | 1336 |
| 6 | 852 | 1336 |
| 7 | 852 | 1209 |
| 8 | 941 | 1209 |
| 9 | 941 | 852 |
These tones are sent to the central office, where they are decoded to determine the number being dialed. This process is much faster than the pulse dialing system, which required the central office to interpret the on-off tones sent by the phone.
Advantages of Touch Tone Phones
There are several advantages to using touch tone phones over pulse dialing phones:
- Speed: Touch tone dialing is much faster than pulse dialing, as it requires fewer steps to send the number.
- Reliability: Touch tone phones are more reliable, as they are less susceptible to line noise and interference than pulse dialing phones.
- Additional Features: Touch tone phones can support additional features, such as caller ID, call waiting, and three-way calling, which are not available with pulse dialing phones.
History of Touch Tone Phones
The first touch tone phones were introduced in the 1960s, and they quickly became the standard for telephones worldwide. The technology was developed by Bell Telephone Laboratories, and it was first used in the United States in 1963. By the 1980s, touch tone phones had replaced pulse dialing phones in most countries.
Modern Touch Tone Phones
Today, touch tone phones come in a variety of styles and features. Some of the most common types include:
- Traditional Corded Phones: These phones are the most common type of touch tone phone and are typically used in homes and offices.
- Cordless Phones: Cordless phones offer the convenience of being able to move around while on the phone, making them popular for use in homes and offices.
