Parts Of The Telephone

First, we will point out the things you can see, and next we will get to what is inside. Here is a diagram of a typical telephone with its external parts labeled.

Figure 1: Parts of the Telephone
  1. The telephone handset, also called the receiver. In fact, it includes both the receiver enabling you to hear and the transmitter through which you speak. It may also have a volume control or a bar that you can depress to mute either the receiving or transmitting capability. (Buttons on the telephone may also control these functions.)

    Handsets come in different shapes and sizes and are usually made to work with a telephone from a specific manufacturer.

    The handset may be directly wired (also called hardwired) to the telephone cord, which in turn is directly wired into the telephone instrument, or there may be a plastic modular connector at one or both ends of the cord.

    People who spend the entire day on the telephone such as customer service representatives, stock brokerage traders and switchboard attendants often use a headset instead of a handset. On many telephones, you must leave the handset attached and "off the hook" while using a headset, which is cumbersome.

  2. The handset cord. Also known as the curly cord. This often gets very twisted which can break or damage the wires inside causing interference (static or "noise" on the line). Holding it up and letting the handset dangle at the end, enabling the cord to unwind, can straighten it out. As mentioned above, most handsets are connected to the telephone with a small plastic modular connector that plugs into a jack opening on the telephone. Some handsets are hardwired into the telephone and cannot be unplugged.

  3. The mounting cord. A straight cord (cable), usually gray or a translucent gray called silver satin. Typical lengths are 6 feet, 9 feet, 13 feet and 25 feet. This cord sometimes has a modular connector at each end, one plugging into a jack opening on the telephone and the other plugging into a jack opening in the wall. In some cases the mounting cord is wired directly to the telephone or the wall or to both and cannot be unplugged.

  4. The dial pad. Also called the keypad, touch-tone pad, touch-tone buttons or DTMF pad ("DTMF" stands for dual tone multi-frequency, referring to the touch-tone signals). Most telephones use the DTMF method for sending a telephone number to the telecommunications service provider. The local telephone company central office and the business telephone system (PBX) must have the capability to process these tones. The telephone is equipped with the dial pad having 12 buttons that represent the numbers 0 through 9 and the symbols * and #. Pressing one of the buttons causes an electronic circuit to generate two tones. There is a low-frequency tone for each row and a high-frequency tone for each column. Pressing button number 5, for example, generates a 770-Hz tone and a 1,336-Hz tone. By using this dual tone method, only seven tones produce 12 unique combinations. The frequencies and the dial pad layout have been internationally standardized, but the tolerances for variations in frequencies may vary in different countries.

    The touchtone signals are used not only to dial telephone numbers, but also to interact with Voice Processing systems such as Voice Mail, Automated Attendant. (for Sales press 1, for Service press 2, etc.) and Interactive Voice Response.

    Some telephones may have a round rotary dial, but this is becoming less common. The signals sent out by a rotary dial telephone are called dial pulse.

    Rotary dial telephones are still in use. In general, their dial pulses are not recognized by voice processing systems. Some of the newer voice processing systems use voice recognition (Say "Yes" for the Sales Department.)

  5. The feature buttons, also known as feature keys or function keys. These can serve a variety of functions. They enable different outside lines and extensions to be answered. They may activate telephone system functions such as call transfer, call conferencing, call forwarding, etc. They can also be used to speed dial frequently called numbers. Every telephone system manufacturer treats these feature buttons differently, so what you learn about one system may not apply to another. Some feature buttons are flexible, meaning that they can be programmed for a variety of functions. Some are fixed, meaning they can provide only a specific function. Some systems have soft keys meaning that the same button performs different functions at different times.

  6. The display, also known as the LCD (liquid crystal display). Not all telephones have displays, although most newer ones do. All business telephone system manufacturers provide them, but the display telephones may cost more. In most cases they are worth the investment since operating the telephone on a business telephone system without the benefit of the information provided in the display can be cumbersome. Different systems provide different information in the display. Some show the date and time when the telephone is not in use. Some provide instruction prompts to the person attempting to use system functions. Most show the name or extension number of the person calling you, if the call is coming from someone else within your office. Some show the name or telephone number of the person calling you from another location (known as Caller ID or ANI - automatic number identification - if this information is being delivered to your PBX over your outside lines.). A few systems enable you to leave a pre-selected message so that when someone calls your telephone from within your office, his display will read that you are "out to lunch" or "in a meeting." Other systems enable a secretary to send a silent message to the boss while the boss is on another call, although this is not common. As with the feature buttons, the important thing to remember is that telephones and telephone systems from different manufacturers use the display differently. No two are exactly the same.

  7. Lights (also called lamps or LEDs - light emitting diodes) On some systems there may not be a light, but an LCD (liquid crystal display) indicator instead. Most people find the lights easier to see than the LCD. The purpose of the light or LCD is to indicate the status of a call in progress on one of the outside lines or extensions. The light may be red, green, white or amber and more than one color may be lit at the same time. This differs considerably depending upon the manufacturer and model of the system. A light flashing on and off slowly may indicate a new incoming call and is sometimes accompanied by an audible ring. If the same extension appears on more than one telephone it may simply flash at some telephones and audibly ring on others. A steady light usually indicates that the line is in use on either your telephone or another telephone that picks up the same line. A rhythmically flickering light may indicate that a call is on hold. Some telephones have a light next to the button of the extension number that remains lit even when the telephone is not in use.

  8. The switchhook. This refers to those two little plastic buttons that press down on a conventional telephone when you hang up the receiver. When you hang up you are actually breaking an electrical circuit that connected you to the person at the other end while you were talking. On some telephones, the switchhook may be a single bar that depresses when you hang up. Other telephones have a magnetic switchhook inside the telephone, directly under the receiver when it is hung up, that cannot be seen from the outside. In very old movies, we often see someone frantically tapping the switchhook trying to get help as the intruder is banging on the front door. This method was once used to reach an "operator" or switchboard attendant. Instead you would now dial 0. In telephone systems introduced in the 1960's and 1970's, the switchhook was used as a means of activating the system functions such as call transfer. If you held the switchhook down for a second too long, you'd disconnect the call! These functions are now accomplished more easily with feature buttons.

  9. Speaker. Most multi-line and a few single-line telephones are equipped with some type of speaker. A speakerphone enables the person using the telephone to have hands-free conversation with another person at a distant location without lifting the handset. Some speakers are one way only. This may be called a monitor rather than a speakerphone, which is two-way. The monitor enables the person using the telephone to dial out or wait on hold without lifting the handset. They can hear what is on the open line, but cannot speak back to the caller without picking up the handset. Another capability, also called monitoring, enables others in the room to hear both sides of a telephone call in progress, while the person in the room who is speaking uses the handset and the caller at the other end does not sense that he is on a speaker. This is sometimes used for training staff members on how to handle particular types of calls. Speakers may also be used for internal intercom communication only, where someone in on the same premises can call you and his voice will be projected over the speaker. Some systems will allow you to answer back hands-free while others will not. Not surprisingly, this feature is known as hands free answer back!

  10. Message waiting indicator. If the system is working with a Voice Mail system, this lamp or LCD indicator lets you know that you have a message waiting in your Voice Mailbox. There may also be a message on the display of the telephone such as MW for "message waiting." Any of these may also indicate a message waiting at the reception desk or message desk if there is no Voice Mail. Although this use is less common most telephone systems enable a receptionist to manually activate a message-waiting indicator on any telephone in the system. In some systems, the message waiting indicator is a button that, when pressed, will automatically connect you to the Voice Mail system or receptionist to retrieve your messages.

  11. Base of the telephone; telephone housing. This is generally a molded plastic casing designed to house a specific type of telephone.

  12. Faceplate or Face Layout. Most telephones that work with business telephone systems enable you to print a layout of the front (face) of the telephone including the extension numbers and system features that correspond to each button. This printed layout may slip into place over the buttons and under a clear plastic cover that is often called the faceplate.


Malc said...

Yes, this is a typical telephone diagram... I'm not sure if Telephone Systems Northeast Mississippi use this phone nowadays...

Lincoln Madison said...

It may also help in building the reputation of the company. It is possible that people assume that businesses that have Toll Free Numbers are getting good profits, and therefore their products and services are good.

pankaj said...

Its very interesting post, good job

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