Telephony Fundamentals
Definition of Decibel
Unit of measure of sound intensity, corresponding to one tenth of a bel, used to express the relationship between two powers.
Amplifier Circuit Gain
An amplifier circuit provides an output of 15 watts with an input signal of 3 watts. Calculate the circuit gain in decibels.
Answer: I do not know.
Unit of dBm
What is the unit of dBm reference?
Answer: Milliwatts (mW).
Crosstalk
What is crosstalk?
Answer: It is the coupling of signals transmitted through a circuit to another nearby circuit. It’s the phenomenon where a signal in one circuit induces interference in another.
Pupinization
What is pupinization?
Answer: It reduces problems in transmission lines by adding loading coils at regular intervals.
2-Wire to 4-Wire Conversion
Why do we need 2-wire to 4-wire conversion in a telephone?
Answer: Telephones use a single pair of wires (2-wire circuits) for both communication directions. Conversion is needed for separate transmit and receive paths.
Hybrid Coil
What element is responsible for 2-wire to 4-wire conversion?
Answer: The hybrid coil.
Connection of Telephone Exchanges and Subscribers
How are telephone exchanges and subscribers connected?
Answer: Switchgear and pairs of copper wires.
Telephone Exchange Connection
What type of exchange are subscribers connected to?
Answer: Local Central.
Hierarchical Level of Telephone Exchanges
Show the hierarchical level of telephone exchanges, from lowest to highest.
Answer:
- Local exchanges
- Primary central stations
- Secondary stations
- Tertiary nodal stations
Direct Sections
What are direct sections?
Answer: Sets of links connecting two exchanges.
Location of Nodal Stations in Spain
Where are nodal stations located in Spain?
Answer: Madrid, Barcelona, Valencia, Seville, Leon, Bilbao.
Telephone Traffic Intensity
What is the telephone traffic intensity in Erlangs for a central office with 43 calls averaging 1 minute each?
Answer: Vt = n x d = 43 x 1 min = 43 / 60 = 0.716 Erlangs.
Types of Calls in a Local Exchange
Indicate four types of calls that can occur in a local exchange.
Answer:
- Local calls
- Outgoing calls
- Incoming calls
- Transit traffic
Space Switching
What is space switching?
Answer: A connection is made through a path formed by different crosspoints set in space.
Time Switching
What is time switching?
Answer: It involves digitizing telephone signals using time-division multiplexing (TDM) techniques.