Materials Used in R&D
The following items constitute a telephone instrument cord. The final requirements of a cable, determine the items used.
The typical conductor used for a telephone instrument cord is called tinsel. In some cases annealed bare copper is also used Tinsel is a special type of Drawn Copper.
A 0.079 mm Copper strand is flattened which is called a ribbon. These ribbons are wound round a yarn to form a core. Many cores are wound to form a strand.
Many cores are wound to form a strand The various types of tinsel used are:
- 4x1 tinsel
- 4x2 tinsel
- 7x1 tinsel
- 7x2 tinsel
Tinsel types used in telephone cords are Plain Annealed Bare Copper or Cadmium copper
Insulation
The type of insulation used for a coil cord, determines many of the cord properties. It is important to use the correct insulation. The insulated conductor determines properties as elongation, retraction, coiling, cable break-load, etc.
Some of the types of insulation materials are:
- Polypropylene - PP
- Polyethylene - PE
- Poly Vinyl Chloride - PVC
- Polyester
Sheath on the Cord
The insulated conductors are placed parallel and over sheathed. The material normally used is PVC. For other applications materials like Poly Urethane (PU) etc., are used.The material preferred is based on temperature, area of usage (internal or external, atmospheric conditions), abrasion requirements, retraction, etc.
Terminations
In most of the countries modular plugs are used as terminations. The other type of terminations that are in vogue are Y terminals, Country specific plugs, etc. The modular plugs are inserted with nickel plated terminals on which
gold plating is done. The gold plating types prevailing in the industry are gold flash, 03u", 6u”, 15u”, 30u”, 50u”. In Europe, most countries have their own type of plugs.
In India, for the BSNL phone the 50u” plugs are
used.
The modular plugs are FCC approved and are available with UL 94 V0 and UL 94 V2 requirements.
Modular Plugs
Gold Plated Plugs
French Plug
Korean Plug-Bottom View
