To provide a reciprocatingly stretchable spring causing no defect in a complicatedly entangled telephone receiver roll cord or portable earphone cord, preventing left-handed phenomenon, even on a sudden brake by a "reciprocating spring" suspension of a vehicle.

A method for forming an S type spring roll and a two types of (reverse) spooling on a roll coil connecting a telephone receiver with a body telephone set and uniting or docking their center O portion to solve the problem of generating a winding twist phenomenon of a defective is provided. In a method for forming a united curl coil with one wire, a contraction force is accelerated with functioning S type curl spring and two types of spring curl to have a reciprocatingly stretchable force and a husky voice on the phone is generated through a function of a spring of a strong recovery force as a defect of the twisting phenomenon. This spring is a reciprocating spring. With the same effect for extending and contracting a telephone of a high quality "connected" telephone call or earphone, an excessively long portable earphone length of 115 cm can be reduced to 18 cm-20 cm for convenient use and the reciprocating spring effect can be formed compact.

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