Tinsel wire

Tinsel wire is a type of electrical wire that is useful where bending occurs frequently and the required current-carrying capacity is low, such as in the cords of wired telephones, wired handsets, headphones, headsets, and other low-power applications. It is far more resistant to failing as a result of metal fatigue than ordinary stranded wire or solid wire.

Construction

The conductor in tinsel wire is several ribbons of metal foil, which resembles decorative tinsel (hence the name). Tinsel wire is produced by wrapping these ribbons around a flexible nylon or textile core and extruding plastic insulation around it. Because the foil is very thin, the bend radius imposed on the foil is much greater than the thickness of the foil, leading to a low probability of metal fatigue. The core provides bulk and tensile strength without reducing flexibility.

Multiple tinsel wires are jacketed into cable. Originally it was round cable, but production changed over to flat cable, for use with modular connectors. (The conductors are not bonded to each other, so it is not ribbon cable.) Round and flat cable can be made straight or curly. Straight cable is used between the wall receptacle and the telephone. Curly cable is used between the telephone and the handset.

The flat cable is then crimped into modular connectors, to make modular cable assemblies (cords) for telephone and other use.

If the jacket is removed, single tinsel wires can be connected to equipment using crimped terminals that pierce the insulation to make contact with the metal ribbons within. Until the emergence of modular connectors, individual connections were used in every telephone and telephone jack. Since then, single connections are far less common, used only where a tinsel-wire cable is permanently attached, usually to save the cost of one modular jack and plug.

Stripping insulation and soldering, common methods of connecting stranded and solid insulated wire, are not as practical for connecting tinsel wire because the ribbons easily break with handling, and the conductors tend to break off later at their junction with the rigid solder. (A failed connection can sometimes be repaired by soldering, but the core and insulation often melt, and reliability afterward is low.)

People never see the tinsel conductors unless they dissect a telephone cord. Even technicians who crimp modular connectors onto flat cable every day never see the tinsel, because there is no reason to strip the conductors.

Applications

Tinsel wire is used in power cords for very small appliances such as electric shavers or clocks, where stranded cable conductors of adequate mechanical size would be too stiff. "Tinsel cords" are recognized as type TPT or TST in the US and Canadian electrical codes, and are rated at 0.5 amperes.