WPCL 2BJ|x ` H   x|@  6'6' Recommendation L.9 )METHODS OF TERMINATING METALLIC TABLE CONDUCTORS 1.HGeneral   HMetallic cable conductor terminations are installed at various locations within the cable network. The type of terminal and termination device utilized in these locations is dependent on various factors relating to the specific installation: H type of cable and conductor being terminated; H location and purpose of the termination; H number or quantity of terminations required; H type of service or transmission link involved; H flexibility and protection requirements.  X HBasically, all exchange, repeater (amplifier or regenerator), and major crossconnection point terminations are of the "fixed" type utilizing wrapping, soldering or insulation displacement connection (IDC) techniques. HLocal distribution and customer terminations utilize a mixture of "fix" and "temporary" (screw terminal) type terminations depending on individual conditions. Where required, overvoltage protection may be provided as an integral component of the terminating device or a separate "addon" facility. HWithin a cable network, two methods of terminating cables are available. These may generally be referred to as the direct and indirect methods. HDirect termination implies that the conductors associated with a particular cable are connected directly to the terminal forming the "end" of the cable circuit, e.g. the cable conductor and terminal are directly coupled. HIndirect termination implies that the cable conductor is connected to the end terminal via a device that incorporates a performed or manufactured termination. HDirect terminations are usually utilized in end terminals such as at the exchange MDF and customer premises, although some direct terminations are used in the customer distribution cable area. In most other midpoint terminations, (distribution cabinets and pillards, repeater housings and termination points for trunk carrier and coaxial cables), indirect terminations utilizing devices with preterminating tail cables are spliced into the basic bearer cables. HThe electric conducting parts of terminating devices will be of metal such as copper, brass or other similar alloys suitably plated to resist corrosion and other environmental effects and provide good electrical connection, either by contact, pressure, soldering or wrapping. HVarious insulating materials, (Plastic extrusions and resin moulding) provide the mechanical mounting and electrical insulation of the metallic components. 2.HTermination types 2.1HTermination types for symmetric pair conductors H Wirewrapping type HIn this type, the conductor is wirestripped and cut inserted in a wirewrap tool and wirewrapped around the terminal point. H Solderon type HIn this type, the conductor is wirestripped and cut inserted in terminal slot and soldered. H Wrap and solder type HIn this type, after wrapping, the conductor is soldered to the cut end of a terminal. H Binder post type HThere are different forms of this type. Ha)  By means of screws. H The conductor is wirestripped, cut and fastened with screws by HHX means of a screw driver.  `  Hb)  By means of nuts.  H H Consist of a fixed threaded brass post containing a washer and a H threaded hex nut. The conductors are terminated between the H8"II"Jwashers. H Insulation displacement contact (IDC) type HIn this type, generally the conductor is installed and pressed into a Uelement contact by means of a special tool. HThe Uelement contact has different forms and is applied mostly to the terminal devices. H Termination for unused conductors HThis termination is made by means of plastic bodies connectors without Uelement contacts, and are used for protection of unused conductors in a pedestal or splice closure. 2.2HTermination types for coaxial conductors H Connectors types HCoaxial pairs are terminated in connectors mounted on a metallic diaphragm for the access to the repeater housing of the terminal equipment. HThe connector splices the stiff coaxial tube to the flexible one into the housing or exchange and is provided itself with a device for pneumatic insulation. H Direct joint type HSometimes, a joint between air core tube and flexible coaxial cable are made. ,Ԍ 3.HTermination use HThe types of termination are used in different devices for terminating cables in all their applications: main distribution frame, regenerating equipments, cabinets, terminal boxes and subscriber's premises. HThese devices present some physical characteristics very different in every country, although their technical features (electrical and environmental requirements) are very similar. 4.HRequirements for MDF terminating devices HThe basic requirements of the exchange MDF terminating device include the provision for: H fixed termination of external cable conductors, in multipair units HHX (usually 100), and associated jumper crossconnection leads;  `   H H ease of termination, and retermination where necessary, of cable and jumper crossconnection conductors; H over voltage protection by addon or plug in of triode gas HHX protectors;  `    H circuit isolation by insertion or removal of an appropriate HHX device;  `    H independent circuit accessing and testing, for equipment and line HHX sides;  `  H circuit paralleling; H earthing points or buses;  8 H ratio of O/G to I/C circuit terminating capability of at least HHX two;  `  H multipoint pair access connection (plugs and leads); H colour coding of special circuits; H fanning strips and jumper guides; H permanent circuit indentification numbering; H good visibility. HTechnical requirements   HThe design, construction and materials utilized in the terminating device must provide for an expected service life of up to 40 years. Devices must be compatible with the existing MDF construction and utilization practices, interchangeable with the existing termination devices, and maintain or increase current circuit density per unit area. HThe line side terminals shall be required to terminate the existing range of copper external cable conductors extending from 0.32 mm to 0.90 mm diameter plastic insulated with solid or cellular forms of insulation. The equipment side terminals shall be required to terminate the existing range of copper internal cable conductors.  H HReliable retermination of conductors in the order of 100 to 200 times over the life of the system shall be possible. Prior termination of larger conductors shall not affect the subsequent termination of a second thinner wire. HThe lineside terminating device on which line cables terminate should allow for the installation and acceptance testing of external cables. (Current automatic simultaneous access, via the MDF termination, to all pairs in each 100 or different pair terminating unit.) HTerminating equipment shall be able to withstand the effects of normal concentrations of moisture, sodium chloride, hydrogen sulphide, sulphur dioxide, ammonium chloride and formic acid which may penetrate or originate in buildings. HTerminating equipment shall be expected to operate satisfactorily in temperatures ranging from 10oC to 50oC with daily ambient fluctuations of up to 15oC. Upper temperature limits shall be assumed to prevail for 25% of total time. Yearly average relative humidity of 75% is to be assumed with maximum values not exceeding 95%. HIn addition to the above, terminating equipment will be required to satisfy the following test requirements: H  cold; H  dry heat; H  damp heat; H accelerated damp heat; H  vibration; H  storage; H  mould growth; H  corrosion test; H  robustness of terminals. HSafety HTerminating systems will need to be designed with safety and security in mind. To this end, designs should:   HH© minimize likelihood of unintended electrical contact and/or accidental dislocation of wires;  `    HH© use plastic materials with an oxygen index of at least 28 determined in accordance with international standards;  `   H HH© use plastic materials which do not emit hazardous fumes or smoke when heated;  `  HH© avoid sharp corners and edges.  ,ԌHElectrical  H HAll the terminating blocks should have good electrical characteristic in order to minimize the risk of personal injury to staff, customers and  public from electrical causes arising from the installation, operation, and maintenance of the devices. HIf necessary recommend good values for: H insulation resistance; H voltage proof test; H capacitance between pairs of terminals. 5.HRequirements for cable termination devices 5.1HElectrical characteristics of terminations HThe main electrical characteristics specified in most of the administrations for termination devices are: H dielectric strength; H insulation resistance; H reflection index (coaxial only); H contact resistance. HThese characteristics are different for coaxial pair terminations, long distance symmetric pair cables and local symmetric pair cables. 5.2HEnvironmental requirements of terminations HThe requirements should be specified at least for 20 years of field operation in stationary use at partially weatherprotected locations. The IEC Standards should be followed: H temperature cycling, lower and upper limits; H change of temperature; H damp heat, steady state; H standard climatic sequence; H 1.dry heat, H 2.damp heat, cyclic, H 3.cold, H 4.damp heat, cyclic, H gastightness; H shock or vibration.