Telephone Instruments and Signals

Telephone Instruments and Signals Presented by: Engr. Micaela Renee Bernardo

The telephone was invented by at least four different people in three different countries 1. Alexander Graham Bell – Scottish American, generally credited as the "winner" in the race to invent the telephone in the period between 1850 and 1876 2. Johann Philipp Reis – German 3. Antonio Meucci – Italian 4. Elisha Gray - American

In 1876, at the age of 29, Alexander Graham Bell invented his telephone Model of Alexander Graham Bell's Telephone

Design sketch of the phone Famous first words: "Mr. Watson -- come here -- I want to see you."

Johann Philipp Reis

“Ein Pferd frisst keinen Gurkensalat.” - Words supposedly spoken by Philipp Reis in testing his new telephone invention.

Das Reis'sche „Telephon” von 1861

"Telephone" (he was one of the first to coin the term) were manufactured by a German firm, and a few more in England.

Antonio Meucci

Meucci’s Teletrofono – speaking Telegraph

Has been denied fame and fortune only because he lacked $250 and because Bell himself rifled the files of a patent office, destroying the evidence of Meucci's invention

Elisha Gray (1835-1901) Elisha Gray, American inventor, who contested the invention of the telephone with Alexander Graham Bell. He invented a number of telegraphic devices and in 1869 was one of two partners who founded what became Western Electric Company

On February 14, 1876, Bell's telephone patent application was filed at the United States Patent Office; Elisha Gray's attorney filed a caveat for a telephone just a few hours later. On September 12, 1878, patent litigation involving the Bell Telephone Company against Western Union Telegraph Company and Elisha Gray began.

1877 First Commercial Telephone

1878 "Coffin" Style Telephone

1882 Western Electric "three box" Telephone

1880s Desk Telephone

Early 1890s Desk Telephone

Mid-1890s Desk Telephone

1890s Strowger Automatic Telephone

1890s Western Electric Common Battery Telephone

1890s Western Electric two box phone

1905 Automatic Electric Strowger Telephone

1900s Magneto Telephone

1910 Western Electric Desk Telephone

1920s Western Electric Dial Telephone

1920s/30s Western Electric Desk Telephone

1940s Western Electric Desk Telephone

1990s Telephone

Main Parts of a Telephone Set: 1.

Transmitter / mouthpiece

2.

Receiver / earpiece

3.

Switch Hook

4.

Dialer

5.

Ringer

Parts of Telephone Switch Hook / Plunger – also called the cradle; has a lever spring that is used to initiate or terminate call 2 States: 1.

On-Hook – the handset setting when the telephone is idle and the switch is open, thus, no dc current flows through the line.

2.

Off-Hook – the condition as soon as the telephone handset is lifted, the switch is closed thus alerting the C.O. to supply a dc current and a dial tone

Parts of Telephone Dialer 2 Methods:

1.

Dial Pulsing or Pulse Dialing – is defined as a momentary on-hook condition that causes loop making and breaking from the telephone set dialer toward the C.O. Commonly used for rotary telephone set. State of Pulse: 1. make – circuit closed/off-hook 2. break – circuit opened/on-hook

Parts of Telephone To transmit a digit, it takes 0.1 second per pulse + 0.5 second interdigital delay time Pulsing speed = number of pulses per second (pps) Pulsing period = make + break pps = 1 / pulsing period

Example: How long does it take to dial the number 681-1725 using pulse dialing having an interdigit duration of 0.4 sec.?

Example: If a switching machine is set to accept pulses at a rate of 10 pulses per second with a 60% break, find the make interval of the switch.

Parts of Telephone 2.

Multifrequency Dialing or Dual Tone Multifrequency Dialing (DTMF) – a method that is normally done by combining two of the frequencies in the voice frequency band where the combined frequencies represent one digit recognized by the C.O. Commonly used for touch-tone telephone set.

Example: How long does it take to dial the number 680-1134 using tone dialing with 0.05 second duration for each digit and 0.05 second duration for interdigit?

Parts of Telephone Comparison between Rotary & Touch-Tone Dialer:

VS.

Uses make and break techniques

Uses combination of two frequencies

Slow Dialing

Fast Dialing

Heavy electromechanical device

Light, mostly electronic device

Parts of Telephone Ringer or Bell: -

device that converts electrical signals from the C.O. to an audible signal alerting the subscriber that a call is in progress

Ringer Circuits: 1.

Classical Bell Type Ringer - is a mechanical bell controlled by an electronic coil

2.

Electronic Ringer - the coil controlled bell is replaced by modern electronic ringing chip and small speaker

Central Office / Local Exchange Carrier The C.O. operates to: 1.

Provide battery (DC voltage) to a telephone. This DC voltage is used to operate the telephone and to determine when a subscriber has gone off or on-hook.

2.

Provide ringing (AC voltage) voltage to a telephone. This AC voltage operates a bell or buzzer in the telephone to alert the subscriber to an incoming call.

3.

Provide dial tone when a subscriber goes off-hook

4.

Accept the digits dialed by the subscriber when off-hook

5.

Provide switching equipment used to connect a subscriber to the telephone number dialed.

Lines and Trunks

Other Carrier

254123 4

LEC

Interconnection trunk

LEC

Interoffice Trunk Subscriber Line 4121234

Exchange Code = 412

Exchange Code = 424

Subscriber Line 4245678

Network Hierarchy

IGF

TOLL SWITCH

LEC

International Gateway Facility – a facility consisting of international transmission, switching and network management facilities which serve as point of entry and exit in the Philippines of international traffic between the national network and point/s outside the Philippines Toll Switch

– facility that route long distance calls over the appropriate facilities, and deliver them to the local switch that serves the number being called

Local Exchange Carrier

– is a regulatory term in telecommunications for socalled local telephone company. It is also referred to as LEC for short

Numbering Concept Two Numbering Scheme as defined by ITU-T (CCITT):

1.

Uniform Numbering – is a scheme in which the length of the subscriber’s number is uniform inside a given numbering area (common is 7 digits). The first three digits identify the local exchange and the last four digits identify the subscriber.

2.

Non-uniform Numbering – is a scheme in which the subscriber’s number varies within a given numbering area

Elements of Telephone Number:

1.

International Access Code

2.

Country Code

3.

Area Code

4.

Telephone Number

Basic Call Progress

1. On-Hook

2. Off Hook

3. Switching

Basic Call Progress 4. Dialing

5. Ringing

6. Talking

Call Progress Tones 1.

Dial Tone – a tone advising that the exchange is ready to receive call information and inviting the user.to start sending call information. Typically, it can be heard for a maximum period of 20 sec

2.

Ring Tone - is a tone returned by receiving equipment that tells a caller that the phone at that end is ringing

3.

Ringback Tone - intermittent audio tone that a caller in a telephone system hears after dialing a number, when the distant end of the circuit is receiving a ringing signal

Call Progress Tones

4.

Busy Tone - an audible or visual signal that indicates that the called number is occupied or otherwise unavailable

5.

Congestion Tone - a tone advising the caller that the groups of lines or switching equipment necessary for the setting-up of the required call or for the use of a specific service are temporarily engaged

6.

Receiver Off-hook signal – creates a very loud tone at the receiver and it’s purpose is to alert the customer that the telephone’s handset has accidentally gone off-hook and must be placed back onto its cradle

Call Progress Tones

TRANSMISSION MEDIUM

MICROWAVE

FIBER OPTIC CABLE XDSL MODEM

8581234

8151234