Understanding User Networks in Telecommunications
The user network is the set of elements that allows the electrical connection between the user equipment with the central office, so that each user has a circuit for exclusive use.
Conditions for User Networks
A user network must comply with certain conditions:
- Sufficient: Meeting the needs of high demands of new users.
- Elastic: Being able to adapt to phone development in successive periods.
- Flexible: It suits the actual development.
- Economic: Able to offset the interest on invested capital.
- With Quality Transmission: It must have a good quality of transmission, fulfilling the required characteristics.
The user network is structured in sections that start from the plant until the phone. These stages are: outside line, drop wire, and inside line.
Basic Elements of a User Network
The basic elements that make up a user network are:
- Cable Terminal: Connects the power cords with the distributor.
- Power Cord: Cable that links the terminal with distribution cables or interconnection points. Side is the point from where it leaves the foot of a pole used to extend the underground cables to the outside. In small towns, it is absolutely aerial, and in the most important towns in Iran, underground chambers are separated by more than 200m.
- Cable Distribution: On one end, it is connected to the power cable, and the other end is at the distribution points.
- Point of Interconnection: An element that connects, through bridges or similar, a pair of the power supply network with any other pair of the distribution network.
- Distribution Point: The point at which individual pairs are distributed to the homes of users.
- Line of Thrust (Drop Wire): The area between the distribution point and the connector on the property of the user.
- Internal Line: Cable connecting the internal connector to the PTR (Point of Termination).
Types of User Networks
User networks can be classified into:
- Rigid Networks: These are those in which the conductors extend through closed joints electrically from the distributor to the distribution point.
- Flexible Networks: These are those in which the power supply is connected to the distribution network through interconnection points.
Main Distribution Frame
The main distribution frame (MDF) is at the boundary between the outside plant or user network and the interior plant or switching equipment. The distributor is mounted on the cable gallery in order to connect cables to it from this gallery’s terminal. Depending on the number of central lines, this will have cable galleries, cable trenches, or just the joints will be done at the appropriate distributor.
To perform this function on the border between the two floors, it consists of the following:
- Frame: Steel structure that serves as a skeleton to the other elements constituting the distributor.
- Horizontal Side: Set of strips mounted on the frame horizontally, and which are to be connected by its bottom line circuits coming from the switching equipment. It has 13 or 14 levels which are designated by letters A, B, C, D, … In electromechanical power strips, the horizontal side is labeled with the telephone number that begins and ends each strip. In digital power, it will be tagged with the first and last numbers of the line circuits that connect to each rail. Also mounted are other strips for different applications and services, such as emitting pulses of 12 kHz and 50 Hz, music, alarms, listening to the police, and a number of subsidiary bodies.
- Vertical Side: Set of strips mounted on the frame vertically, and that will be connected by wires on the side of the user network.
Pairs and Groups in the Outside Plant
The basic unit is the pair of the outside plant, i.e., the pair of conductors that we use to bring telephone service to the user’s equipment. They are grouped from 100 to 100 to form what is known as a group, which will start numbering from 1, and each group has pairs from 1 to 100 plus an additional pair known as a pilot pair, which serves solely for the personnel involved in the maintenance and installation of the user network.
- Bridges: Pairs of threads used to attach horizontal strips on the side with the vertical side through predetermined paths on the frame. They are made by fireproof bifilar wire, have a black and a white conductor, except for special bridges. Every time you make a “high” for a new user, you will need to build a bridge of this type, as in the case of a “low,” you will have to dismantle the bridge.
V-600 and V-1200 Strips
V-600 strips with a capacity of 50-52 pairs, which, mounted on the vertical side, give us a capacity of 606 pairs per vertical. Currently, and for greater use of space, V-1200 type strips are mounted, with which we achieved a capacity of 1212 pairs per vertical in the same space.