Understanding Telephony Systems: Types, Components, and Installation
Understanding Telephony Systems
Depending on the physical environment in which transmission is performed, telephony can be fixed, by wire, or by electromagnetic radiation.
Central Switching
Central switching is the element responsible for properly redirecting the transmission.
Interior Installation of Subscriber Telephony
The physical connection that allows each of the telephone terminals to connect to the line. Depending on the technology used for the transmission of information, it can be:
- Analog: Usually known as the Public Switched Telephone Network (PSTN).
- Digital: Known as the Integrated Services Digital Network (ISDN).
To provide a minimum number of services, whether digital or analog, the installation should have:
- PTR: Point Network Terminal
- PAU: User Access Point
- A rosette connection
Telephone Cables
Telephone Cables Used in Indoor Facilities
Indoor telephone cables used in facilities, with a specified number of pairs of wires, can range from 1 to 4 (i.e., 2 to 8 wires).
- Bipolar-Parallel Cable: Typically used for surface facilities but can also be used embedded. It is cream-colored, the rigid copper conductors are 0.5 mm in diameter, and it has one pair.
- Flat Cable: This type of cable can have between 2 and 8 flexible copper wires of 0.5 mm. It is widely used for constructing connecting terminals and telephone cords. The exterior is cream-colored, and it can also be found in gray, white, or black.
- Round Cable: This type has a large number of pairs of wires. Each wire is twisted together to form a pair. It is used for connections between elements in an indoor installation. The wires are 0.5 mm in diameter.
Connections
The union of wiring to the devices that make up a telephone system can be done:
- By RJ connectors
- Direct connection via screw terminal
- For connection strips distributed by insertion
RJ Connectors
These standard connectors allow telephone devices to connect to each other easily and without any tools.
- RJ-9: It has 4 connecting roads and is very small. It is used for constructing the handset cord.
- RJ-11: Possibly the most widespread in analog telephone facilities. It is used for the union between terminals and the rosette and has 6 ways.
- RJ-45: This connector is widely used in computer networks but also used in digital telephony installations larger than the previous ones.
Crimping Tools
Special tools are used for connecting the RJ connectors.
PTR (Point Network Terminal)
An electronic device that has the mission to:
- Define the user with the installation of the operating company.
- Protect the subscriber’s installation from surges.
- Remotely diagnose the operation of the line for the company’s technical service operator.
PAU (User Access Point)
An electromechanical device that allows to:
- Define the user installation and the operator.
- Locate and repair breakdowns.
- Isolate the subscriber’s installation from the overall distribution network.
Inside a PAU, you can find the following:
- A set of terminals for connecting input telephone lines.
- A set of terminals for connecting the rosettes of connection of telephone terminals.
Canalization and Assembly of Interior Telephone Installation
Mounting telephony installations can be done in different ways:
- Surface Installations: This type of installation is ideal for refurbishment and extension as it requires no work. It can be done with cable channels and exterior surface installations.
- Built-in Installations: This is the most used for interior installations. It consists of making chases or holes in the wall at the time of the work to locate tubes and boxes of mechanisms.