1. Field of the Invention
The present invention relates to electric connectors and, more specifically, to a wiring block and cover shell arrangement for use in an electric connector, which keeps the twisted pairs respectively connected to the respective wire clamps at the same distance, so as to have same delay skew, ensuring the unity of signal and, preventing the occurrence of error codes.
2. Description of the Related Art
Transmission of data between electronic apparatus can be achieved by any of a variety of interfaces including electric pulse, cable carrying pulse, and connector connecting computer and apparatus. FIG. 1 illustrates an electric connector for this purpose. This structure of electric connector is comprised of a jack 6 and a plug 7 matching the jack 6. The jack is normally installed in a control panel, printed circuit board, or a wall, having a wiring block 61 to which a cable 5 is connected. The plug 7 has one end connected to a cable 8 and the other end connectable to the jack 6. The subject of the present invention pertains to the wiring block 61.
Referring to FIG. 1 again, the cable 5 is comprised of four twisted pairs. Each twisted pair includes two insulated wires 51 twisted together. Each insulated wire 51 comprises a wire conductor (copper wire) and an insulator covering the wire conductor. During installation, the insulators of the insulated wires 51 of the cable 5 are stripped off at about 5 cm (about 2 inches) from the end, and then the insulated wires 51 are respectively engaged into respective wire clamps 4 in the wiring block 61.
Because a high-speed network transmits signal through the four twisted pairs at the same time, a great delay skew (propagation delay time difference) among the twisted pairs affects the unity of signal and, may cause the occurrence of error codes. Therefore, it is necessary to calculate the time difference between the transmission in the twisted pair having the longest propagation delay and the transmission in the other three twisted pairs. Because the pitch of each twisted pair is different, the propagation delay (the time used in each twisted pair from start of signal transmission to receipt of signal at the other end) in every twisted pair is different. Therefore, the propagation delay skew between twisted pairs was never taken into account. However, in next generation wire materials, metal shield is used, and the twisted pairs have the same pitch, and therefore the propagation delay skew becomes important. Because every twisted pair transmits differential signal, the propagation delay skew among the wires of each twisted pair is important.
As illustrated in FIG. 2, because the wire clamps 4 are arranged into two parallel rows, the four twisted pairs cannot be respectively connected to the wire clamps 4 at an equal distance. Therefore, the time used in each twisted pair from start of signal transmission to receipt of signal at the other end is different, i.e., the propagation delay in each twisted pair is different. Excessive delay skew affects the unity of signal and may produce error codes.
Further, because the insulated wires 51 and the wire clamps 4 are intersected and the wire clamps 5 cut through the insulators of the insulated wires 51, the insulated wires 51 do not slip in longitudinal direction. However, the clamping force of the wire clamps 4 cannot effectively prohibit displacement of the insulated wires 51 in the axial direction of the respective wire clamps 4, i.e., the connection between the cable 5 and the wiring block 61 is positive.