Wire Lines Research Articles

Open Wire Carrier Working

This section mainly deals with the performance standards for carrier systems on open wire lines.

Line-Fishing on the Continental Slope III. Mid-Water Fishing with Vertical Lines

INTRODUCTIONThe results of bottom line fishing have shown that significant catches can be made down to 3000 m depth at several positions on the continental slope off south-west England (Forster, 1968). But when hooks were lifted off the bottom either deliberately or accidentally very few fish were taken. The chances of catching bathypelagic fish in mid-water by baited hooks therefore seemed slender. In 1966 when thin white lines were tried, they were bitten through several times, always at about 1100 m depth. Trials with baited hooks set on thin wire lines in 1967 showed that the black scabbard fish Aphanopus carbo could be taken at this depth. In 1968 and 1970 during the course of short voyages on R.V. ‘Sarsia’ further vertical line hauls were made, taking Aphanopus regularly and also two species of deep-water squaloids.

Some Features of the HC-278 Modem

The recently developed HC-278 digital data modem provides full-duplex data transmission at rates up to 1200 bit/s over voice bandwidth channels in fixed or transportable ground electronic systems. Using phase continuous frequency shift modulation, the modem meets the operational requirements of JCS Publ. 10 (TADIL-B) and the interface requirements of MIL-STD188B. Suitable transmission channels include wire lines and tropospheric scatter radio equipment. Maximum usage of digital techniques and integrated circuits provides economy, reliability, simplicity, and compactness. The modulator accepts synchronous serial digital data at standard rates of 75, 150, 300, 600, or 1200 bit/s and converts the bits into tones representing MARK frequency (logical 1) and SPACE frequency (logical 0). At the receiving terminal, the composite line signal containing the above tones is decoded into the original serial bit stream. System timing is derived from a crystal oscillator with a frequency of 1.0752 MHz and stability of 1 \times 10^{-7} per month.

Multiple base transmitter synchronization

Three experimental 150 MHz transmitters, located about Albany, New York, have been slaved to a common synchronizing signal by means of phase-lock techniques and wire lines. By achieving excellent, long term relative stability, routine frequency adjustments and annoying beat frequencies are eliminated. Details and performance of a modular system, which makes available any number up to 11 assigned channels, are discussed.

Coupling between Open and Shielded Wire Lines over a Ground Plane

Convenient expressions are derived which permit accurate determination of induced interference in open (unshielded) wire and shielded wire (or coaxial) lines due to ac and transient currents. Curves and tables are presented for obtaining key parameters in the calculation of interference. The limitations of the derived expressions are set forth and an example interference problem is solved. Experimental verification of the analysis is presented.

Square-Law Detector Performance in an Impulsive Noise Background

The purpose of this correspondence is to report on some nxasurements of output SNR (signal-to-noise ratio or S/N), characteristics for a square-law detector extracting signals from non-Gaussian noise, specifically, impulsive noise. Non-Garlssian noise arises in varioas communication media such as the atmosphere, wire lines, and under water. In experimental and theoretical investigations of the effects of non-Gaussian noise on various communications systems, a simple correlator is often considered because it is possible to obtain theoretical predictions of the (S/N), for signal and additive non-Gaussian noise at the correlator input if an appropriate noise model is available for calculating the required fourth-order moment. Middleton (1962), in his analysis of correlator performance in non-Gaussian background noise, employed the so-called Poisson impulse noise model. His theoretical predictions reveal that impulsive noise always degrades the (S/N), as compared with Gaussian noise backgrounds having the same spectral distribution for a given input SNR. However, his theoretical formulas are rather difficult to check experimentally in their full generality and assess the relative importance of various parameters. We compare a study restricted to the case of a square-law detector with Middleton's results.

Wire and strip delay lines

Many applications exist, in radar and computers especially, for cheap large-capacity stores, for which wire and strip delay lines are widely used. They offer stores of up to 20,000 bits and an almost perfectly stable delay, which is important in recirculating memories

Acoustic delay lines— A survey of types and uses

In each issue this year there will be an article on ultrasonic delay lines. This introductory paper will be followed by articles on solid delay lines and the piezoelectric transducers for them; wire, tape and photoelastic lines; and v.h.f. lines. Applications of each type will be described but the accent will be on principles. If necessary further papers will be added to cover particularly important uses more fully

The duobinary technique for high-speed data transmission

A new data transmission technique has been evolved, which has the speed capability of the quaternary systems and, at the same time, promising performance. An important advantage of this technique is that the amount of circuitry required and the degree of complexity are relatively low, being not much more than for a straight binary system and much less than for a typical quaternary system. The process is sufficiently general so that it is applicable to serial transmission over wire lines and parallel transmission over high-frequency radio circuits.

On the Potential Advantage of a Smearing-Desmearing Filter Technique in Overcoming Impulse-Noise Problems in Data Systems

It has long been recognized that impulse noises or even very short duration line interruptions are the most vicious form of interference affecting data communications over wire lines. These noises, while annoying, are not catastrophic in voice communications because of the inherent redundancy in speech sounds. If a degree of apparent redundancy can be inserted into a data stream, the serious degradation caused by these noises can be materially reduced. Data signals which require a sizable bandwidth can be transmitted by modifying the real time placement of their frequency components (smearing) before transmission through a channel corrupted by impulse noises. A reversal of the time-vsenergy frequency modification before detection (desmear) reconstructs the data signal but "smears" the impulse or line interruption into a time-energy distribution form considerable different from that of the signal.

Path Loss Measurements vs Prediction for Long Distance Tropospheric Scatter Circuits

Before any communications circuit can be established between two points, whether it be by wire lines, or by tropospheric or ionospheric radio propagation, a thorough knowledge of the intended path should be obtained so that an efficient and economical installation can be made. Each system should have as high a reliability as is required for its intended use. Tropospheric forward scatter circuits have established their place in the worldwide communications network of the military and it is the intent of this paper to illustrate by a specific example how the performance of a circuit of this type may be predicted with adequate accuracy without making costly transmission loss measurements over the intended path.

Measured Performance of the Sebit-25 Data System Over Wire Line Facilities at 2500 Bits per Second

This paper discusses the actual performance of a 2500 bit per second data modem under simulated conditions in the laboratory and actual conditions on 27 different voice frequency wire lines. Under simulated conditions, it was determined that an error rate of one in 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">6</sup> can be maintained with a signal-to-white noise of 14.5 db. On actual line tests for over 200 hours, the error rate was approximately two hits per hour. The paper includes seven curves illustrating measured results.

Additional frequency errors due to the transmission of electrical oscillations

Existing data shows that all the elements of the circuit, whether propagating or transforming oscillations, introduce frequency errors in the transmitted signals. The relative errors due to the frequency divider is 10−8 to 10−10 and frequency multipliers 10−12 to 10−13[5]. Wire lines introduce an error of 1 · 10−8 to 1 · 10−9, depending on their type and the frequency transmitted.

Precision carrier frequency control and modulation phase equalization of base transmitters in a mobile radio system

Distortion-free reception by mobile units of base transmissions is essential in multiple base station mobile radio systems, where adjacent stations are operated simultaneously and modulated with the same intelligence. Phasing and heterodyne distortion factors in overlap coverage areas must be minimized. After many months of laboratory and field testing, a satisfactory solution has been developed and applied to a system using wire lines for base station and control point interconnection. This method provides precision control of carrier frequencies, and phase equalization of modulation by building out the wire lines so that transit times are equal. After two years of operation this method has proven to assure satisfactory distortion-free reception.

A New Carrier System for Rural Service

A study of the problem of providing telephone service to rural customers indicated the need for a flexible carrier system that could be used economically on new and existing rural cable and open wire lines. The desire for low cost required new approaches to almost every phase of the carrier system design for rural service, which has been designated Type P1. Use of transistors led to sweeping changes in the detailed circuitry and also created demand for other new components. Mounting and interconnecting the circuit components by means of printed wiring boards emphasized the necessity for close coordination between design and manufacturing objectives. The low power-drain requirements of transistor circuitry were supplied economically by the use of similar solid state devices, a new storage battery, and efficient packaging A fast, accurate and simple method has been evolved for applying the P1 carrier system to rural lines with a minimum of line treatment or rearrangement. Plug-in equipment, readily accessible test points, and a carrier test set provide the ease of maintenance needed in the use of telephone equipment at remote locations. Use of the P1 carrier system will extend the application of electronic equipment outside of the telephone central office and provide a carrier system whose performance will be consistent with requirements for high quality communication service at low cost

Open Wire Lines

The properties of two-wire lines and single wire lines (surface wave transmission lines) are discussed on a comparative basis. The two-wire line is actually a system of two coupled single wire lines and thus requires a high degree of symmetry to maintain the desired wave mode. While the single wire line is more affected by bends it has the advantages that it is simpler in construction and is less susceptible to weather conditions. The main domain of the two-wire lines lies in the frequency range below 100 mc and that of the single wire line in the range above 100 mc.

A new 4-channel open-wire carrier system employing transistors

AMONG independent telephone companies, Bell System operating companies, and railroad communications systems, carrier is used to exploit fully the vast mileage of open-wire telephone plant. Consistent with circuit needs, wire lines were first used to transmit voice-frequency circuits and, later, with added transpositions, to transmit carrier circuits employing frequencies to about 35 kc. Even now, after more than 30 years of such growth, however, the great majority of open-wire message traffic for short- and medium-haul distances is transmitted at carrier frequencies below 35 kc. The number of circuit miles in these carrier frequencies is now in the millions. Continued major growth is expected in open-wire plant, not by adding more wire lines but by moving to higher frequencies.

A portable telegraph bias and distortion measuring instrument

IN THE modern telegraph system, signals are transmitted over various trunk facilities derived from wire lines or radio relay systems. The trunk telegraph channels furnish facilities between a number of switching centers located at strategic points throughout the country. These centers then distribute traffic to the local points of destination. In addition, various other services must be accommodated by suitable network configurations. These services comprise such arrangements as are involved in leased network circuits, private switching systems, etc. It is necessary that flexibility be maintained in this complex network of circuits so that circuit patching and routing may be accomplished without making undue alignment changes in the circuits themselves.

Application and transmission features of a new 12-channel open-wire carrier system

A new, miniaturized, 12-channel open-wire carrier system, the Lenkurt 45A system, is described. For use in the 40-to 150-kc frequency region, it co-ordinates fully in level and frequency allocations with present Lenkurt 42C and Western Electric J carrier systems using this frequency space. Because of the inclusion of 2-pilot regulation for flat and slope gain control, supplemented by channel regulation with a range of about ± 7 decibels (db), more stable circuit operation is obtained than in previous open-wire carrier systems. The design which results is much reduced in cost as compared to past systems in this frequency range, and affords an opportunity for considerable expansion in use of open-wire plant above the 35-kc range. This use is further enhanced by optionally supplied compandors, permitting many instances of use of wire lines transposed only for 35-kc operation. An important feature of the system is terminal design and frequency allocation co-ordinated for open-wire, single cable, and radio use. This permits great flexibility in interconnecting among such systems without need for intervening terminals. Miniaturization carried to a high degree results in a terminal occupying but 31 1/2 inches of vertical space on a telephone-type relay rack. Back-to-back operation permits as many as 96 channels in two 11-foot 6-inch bays. Extensive use is made of standardized plug-in units further supplemented by plug-in band filters and signaling options, to fit a wide variety of application requirements.

Television distribution over short wire lines

Television distribution over short wire lines