At&t Bell Laboratories

Bell Telephone Laboratories

American Telephone & Telegraph Co., At&t Bell Laboratories

At&t Technologies, Inc.

At&t Technologies Inc., At&t Bell Laboratories

Wendell G Nutt

Harold Wayne Friesen

Richard D Beggs

Stephen Taylor Zerbs

Larry L Bleich

Luc W Adriaenssens

Francis J Mullin

David M Mitchell

Palmer D Thomas

Kenneth B Parks

George Harry Webster

Janice Bilecky Haber

Keith A Gossett

Todd A Rhoades

Mark E Roach

Joseph P Savage, Jr

Methods and apparatus are provided for providing an electrically matched pair (20) of insulated metallic conductors (21, 21). Insulation is applied to successive portions of a length of wire-like metallic conductor (22) after which a colorant material (37) is applied to the surface of a plastic insulation material of a first portion of the length of the metallic conductor which is being moved along a path of travel. Facilities are provided for shielding a supply of the colorant material from the moving insulated metallic conductor and for then exposing a second portion of the length of the insulated metallic conductor to a different colorant material. The insulation and the colorant materials and their disposition with respect to the insulation are such that the dielectric constant of one insulated metallic conductor of the pair is substantially equal to that of the other. The first and second portions of the length of the insulated metallic conductor are separated from each other and are twisted together to provide an electrically matched pair.

Method of making twisted pairs of insulated metallic conductors for

Methods and apparatus are provided for providing an electrically matched pair (20) of insulated metallic conductors (21,21). Insulation is applied to successive portions of a length of wire-like metallic conductor (22) after which a colorant material (37) is applied to the surface of a plastic insulation material of a first portion of the length of the metallic conductor which is being moved along a path of travel. Facilities are provided for shielding a supply of the colorant material from the moving insulated metalic conductor and for then exposing a second portion of the length of the insulated metallic conductor to a different colorant material. The insulation and the colorant materials and their disposition with respect to the insulation are such that the dielectric constant of one insulated metallic conductor of the pair is substantially equal to that of the other. The first and second portions of the length of the insulated metallic conductor are separated from each other and are twisted together to provide an electrically matched pair.

Twisted pairs of insulated metallic conductors for transmitting high

A fire-resistant cable (20) which is suitable for the transmission of high frequency signals in a local area network includes a core which comprises a plurality of twisted pairs (22,22) of insulated conductors (24,24) and a jacket (35). Each insulated conductor of each pair includes an elongated metallic member (26) and an insulation system (28). The insulation system which is characterized by a suitable low dissipation factor includes dual layers, an outer one of which includes a flame-retardant plastic material. Also, the insulation system is characterized by a suitably low dielectric constant and by compatibility with a relatively short pair twist scheme. In one embodiment, the insulation system includes an inner layer (30) of a polyolefin plastic material and an outer layer (32) of a flame-retardant polyolefin plastic material. The jacket comprises a plastic material characterized by a suitably low dissipation factor and dielectric constant and in a preferred embodiment comprises a flame-retardant polyolefin plastic material. Preferably, the twist length of each pair does not exceed the product of about forty and the outer diameter of an insulated conductor of each pair.

Fire-resistant cable for transmitting high frequency signals

An aerial service wire (20) includes a jacket (40) having a generally rectangularly shaped cross section and comprising a polyvinyl chloride plastic material. Enclosed by the jacket are two groups of strength members (36--36) each of which includes a plurality of filaments and each of which is impregnated with a material which is compatible with that of the jacket. The strength members are disposed along axes (52,54) of the cross section which are normal to an axis (42) which passes through a geometric center through which a longitudinal axis (50) of the jacket passes. Conductors (30--30) which are individually insulated are disposed adjacent to the longitudinal axis with each strength member being disposed between the conductors and the outer surface of the jacket.

Aerial service wire

A balanced mode transmission system (20) for use in a local area network includes at least one twisted pair of insulated metallic conductors (27--27) which at its end is connected through a transformer to a transmitting computer and to a receiving computer (48). Each pair of conductors adjacent to the transmitting end and optionally adjacent to the receiving end is provided with a longitudinal choke (56,57). Also, a longitudinally extending metallic wire (60) is included in the system and is connected possibly through a resistor to ground at each end. The combination of the longitudinal choke at least adjacent to the transmitting end and the longitudinally extending metallic wire is superbly effective in suppressing electromagnetic interference notwithstanding the absence of shielding.

Communications transmission system including facilities for suppressing

In a system (20) for transmitting voice and data signals, insulated metallic conductor pairs (44--44) which transmit data signals and insulated metallic conductor pairs (46--46) which are capable of transmitting voice signals are enclosed in a common sheath system of a single cable (40). User pickup of station apparatus (34) during the generation of a ringing voltage on a voice conductor pair causes that pair to become disturbing and to impart impulse noise to a closely coupled data pair. The data pair is designated a disturbed pair and the signals transmitted thereby may be affected adversely. This problem is overcome by providing a circuit (80) comprising in parallel a resistance and an inductance and being in series with the station apparatus. Such an arrangement reduces substantially that frequency content of any disturbing signal which appears on the disturbing pair and which is in the range of the data signal spectrum. This reduces the magnitude of crosstalk between the voice and data pairs and results in substantially error-free transmitted data.

Methods of and apparatus for providing substantially error-free

A cable (20) which is particularly suited to the transmission of substantially error-free data at relatively high rates over relatively long distances includes at least two pairs of individually insulated conductors (42--42). The pairs of individually insulated conductors are enclosed in a tubular member (51) comprising a plastic material. A metallic shield (54) may or may not enclose the tubular member, and in a preferred embodiment, a plastic jacket (58) is provided. The twist length of each pair of insulated conductors does not exceed a value equal to the product of about forty and the outer diameter of the plastic insulation. Further, the twist lengths among the conductor pairs are varied in accordance with a twist frequency scheme modulated by non-uniform increments of twist frequency.

Local area network cabling arrangement

A cable (20) which is particularly suited to the transmission of substantially error-free data at relatively high rates over relatively long distances includes at least two pairs of individually insulated conductors (42--43). Each pair of individually insulated conductors is enclosed individually in its own tubular member (51) comprising a plastic material. A metallic shield (60) encloses the tubular members, and in a preferred embodiment, a plastic jacket (80) encloses the shield. In the preferred embodiment, two pairs of voice communications conductors are disposed at opposed locations between the shield and the jacket. The thickness of the tubular member is such that each insulated conductor of each twisted pair is caused to be spaced from the shield a distance which is not less than one half the diameter of the metallic wire portion of each pair enclosed by the tubular member.

Local area network cable

A parallel data transmission system (20) comprises a cable (40) which is capable of balanced mode transmission but which is driven in an unbalanced mode. The cable includes a plurality of twisted pairs of individually insulated conductors (42--42) enclosed by a metallic shield (54). The twist lengths are relatively short to cause the pairs to be decoupled sufficiently from one another to allow substantially error-free, parallel transmission over relatively long distances. Interposed between the core and the shield is a spacing member (52) which has a relatively low dielectric constant. Receiving facilities are provided for detecting whether the level of transmitted signals is above or below predetermined threshold values and for converting the received signals into one of two or more logic levels. Advantageously, this system increases substantially the distances over which substantially error-free transmission in an unbalanced mode can be accomplished.

Data transmission system

A multipair telephone cable (50) has been specifically developed for voice frequency and T1 carrier frequency transmission between cities. The copper wire gauge, dielectric diameter, and insulation expansion are uniquely designed so that this single cable design can be used for either air core or waterproof versions of the cable. Advantageously, both cable versions are compatible with existing carrier and voice frequency electronics. Also, the load coil spacing for voice frequency transmission and the regenerative repeater spacing for carrier transmission coincide in both versions.

Telecommunications multipair cable

While randomized splicing of twisted conductor pairs within groups in pulp cables is generally desirable to avoid electrical degradation resulting from systematic additions of capacitance unbalances, restoration of such cables, when severed, requires identification of each conductor pair for splicing. A cable design with a restoration color code has been developed which features groups having a manageable number of conductor pairs for identification splicing. Each group comprises several conductor pairs which have unique color combinations and which are precisely arranged in the group so the remaining conductor pairs having repeating color combinations can be identified by position relative to the uniquely colored pairs.

Cable design with limited color coding

A multipair telephone cable especially designed to carry interoffice traffic consists of copper conductors insulated with expanded plastic with or without a solid plastic skin. The copper gauge size, insulation expansion factor and dielectric diameter are uniquely designed to consume a minimum of cable cross-section area while permitting use of the cable to provide voice frequency circuits in a manner comparable to normal; 24-gauge cable as well as to provide carrier frequency circuits operating in the range of from about 100 kHz to 8.0 MHz comparably to normal 22-gauge cable. The cable includes pairs twisted according to a constant twist frequency spacing concept.

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Dunwoody, GA, United States of America

Wendell G Nutt