THE MEANING OF TELECOMMUNICATION

1. THE MEANING OF TELECOMMUNICATION Telecommunication is the exchange of information over a significant distance by electronic means. A complete, single telecommunication circuit consists of two stations, each equipped with a transmitter and a receiver. The transmitter and receiver at any station may be combined into a single device called the transceiver. The medium of signal transmission can be electrical wire or cable (also known as copper) optical fiber or electromagnetic field. The free space transmission and reception of data by means of electromagnetic field is called wireless. The term “Telephone Service within an estate” shall be deemed to mean any communication service for the transmission or reception of voice, data, sound, signals, pictures, writing, or signs of all kinds by wire, fiber, radio, light, or other visual or electromagnetic means, and shall include all telephone lines, facilities, or system used in the rendition of such service; but shall not be deemed to mean message telegram service or community antenna television system services or facilities other than those intended exclusively for educational purposes, or radio broadcasting services or facilities within the meaning of section 153 (0) of title 47. 2. IDENTIFY THE AUTHORITIES RESPONSIBLE FOR TELECOMMUNICATION IN NIGERIA? a. The Nigerian Communication Commission (NCC) is the independent National Regulatory Authority for the telecommunication industry in Nigeria, established by degree number 75 by the Federal military Government of Nigeria on 24th November 1992. b. The Nigerian Broadcasting Commission, established in 1992 (NBC) ¬¬¬¬¬¬¬¬¬3, SUBSCRIBERS OF TELEPHONE EXCHANGE IN REAL ESTATE. A telephone exchange is a telecommunications system used in the public switched telephone network or in large enterprises. An exchange consists of electronic components and in older systems also human operators that interconnect (switch) telephone subscriber lines or virtual circuits of digital systems to establish telephone calls between subscribers. 1 In the public telecommunication networks a telephone exchange is located in a central office (CO), typically a building used to house the inside plant equipment of potentially several telephone exchanges, each serving a certain geographical exchange area. Central office locations are often identified in North America as wire centers, designating a facility from which a telephone obtains dial tone.[1] For business and billing purposes, telephony carriers also define rate centers, which in larger cities may be clusters of central offices, to define specified geographical locations for determining distance measurements. In the United States and Canada, the Bell System established in the 1940s a uniform system of identifying each telephone exchange with a three-digit exchange code, or central office code, that was used as a prefix to subscriber telephone numbers. All exchanges within a larger region, typically aggregated by state, were assigned a common area code. With the development of international and transoceanic telephone trunks, especially driven by direct customer dialing, similar efforts of systematic organization of the telephone networks occurred in many countries in the mid-20th century. For corporate or enterprise use, a private telephone exchange is often referred to as a private branch exchange (PBX), when it has connections to the public switched telephone network. A PBX is installed in enterprise facilities, typically collocated with large office spaces or within an organizational campus to serve the local private telephone system and any private leased line circuits. Smaller installations might deploy a PBX or key telephone system in the office of a receptionist. 4. TELEPHONE LOCAL LINE NETWORK Depending on their structure and function, telephone networks in the USSR, as in many other countries, are subdivided into local (rural and urban), area, interarea, long-distance, and international networks. With rural telephone networks, each local central office serves between 50 and 200 subscribers. The local offices are interconnected through a tandem office, and the tandem offices are linked through a central tandem office to a toll office (Figure 1). Urban networks having more than one central office are divided into districts. When the districts are fairly small, that is, serving only tens of thousands of subscribers, the district central offices are interconnected, and each one is linked to a 2. toll office. In larger systems, where each district serves hundreds of thousands of subscribers, lines are used more efficiently and multiplexing is more effective when the district offices are linked to the toll office through a tandem office. Usually, the territory of a country is divided into areas according to a numbering plan. The number of areas ranges between 50 and 200, with the USSR having (1975) 160. Each area will have one or two toll offices to handle the incoming and outgoing calls of that area’s local central offices. The toll office or offices, together with the communications lines interconnecting the toll office or offices with the local central offices, constitute an area telephone network. Together, a country’s area telephone networks constitute an interarea telephone network. A long-distance telephone network is formed by a country’s toll offices, control switching points, and interconnecting communications lines. The control switching points are designed to make indirect connections and to map out alternate routes. In telephone networks where central offices are connected to offices of higher rank, direct interoffice trunks can be used to link any two offices when warranted by the volume of traffic. The introduction of control switching points and tandem offices has made possible a substantial reduction in the number of direct interoffice trunks needed to handle all calls in a given direction with a specified quality of service. A quality of service can be maintained wherein no more than 1 percent of the calls are blocked by busy circuits. An international telephone network is farmed by all international offices, transit centers for international, including intercontinental calls,and interconnecting communications lines. Development work on telephone networks is geared toward increasing the level of automation in setting up connections at central offices and switching points and introducing automatic central offices and control switching points that do not need constant maintenance. These offices and switching points will be either electronic or quasi-electronic. With the latter, the control apparatus is made up of electronic components, and the switching of communications lines is done by small, high-speed telephone relays, such as hermetic contacts. Work is also being done on developing adaptive automatic control systems for telephone networks. These systems include devices for representing, monitoring, and correcting the condition of a network; the devices, acting upon information (the dialed number) received from the caller, search the network for the optimum route of setting up the connection. Microelectronics and electronic control computers are being used in 3. telephone equipment. The telephone network in the USSR is being developed as part of the Integrated Automatic Communications System. 5. DESCRIPTION OF TRUNK NETWORK This article is about the network-design strategies. For riding in auto cargo space, see Trunk (automobile)Trunking. For the UK term for electrical wireways, see Electrical conduit#Trunking. A diagram of a hierarchical communications network. Blue: main lines; red: feeder lines. In telecommunications, trunking is a method for a system to provide network access to many clients by sharing a set of lines or frequencies instead of providing them individually. This is analogous to the structure of a tree with one trunk and many branches. Examples of this include telephone systems and the VHF radios commonly used by police agencies. More recently port trunking has been applied in computer networking as well. A trunk is a single transmission channel between two points, each point being either the switching center or the node. There are several apparent influences on the use of the "trunking" term in communication networks. The most elemental ones are the natural models of a tree trunk and its branches; tributary streams' confluence with rivers; and river deltas' branching of channels. The term's previous use in railway track terminology (e.g., India's Grand Trunk Road, Canada's Grand Trunk Railway), which came from the natural models mentioned above, is another likely influence. Railway networks, with trunks, branches, and switches, were a contemporary model for many decades of the development of telegraph and telephone networks. In fact, turnover of employment among engineers in the railroading and telecommunications industries was not unusual during these decades, which makes the use of these analogies unsurprising. For example, Theodore Newton Vail had been a manager of railroad networks before he became an architect of telephone networks. 4. Another possible explanation is that, from an early stage in the development of telephony, the (up to around 10 cm diameter) containing many pairs of wires. These were usually sheathed in lead. Thus, both in colour and size they resembled an elephant's trunk. The elephant's-trunk hypothesis may be a false etymology. 6. PREPARE A LAYOUT PLAN FOR TELEPHONE EXCHANGE A modern exchange, equipped not just for voice communication but also for broadband data. A telephone exchange is a telecommunications system used in the public switched telephone network or in large enterprises. An exchange consists of electronic components and in older systems also human operators that interconnect (switch) telephone subscriber lines or virtual circuits of digital systems to establish telephone calls between subscribers. In the public telecommunication networks a telephone exchange is located in a central office (CO), typically a building used to house the inside plant equipment of potentially several telephone exchanges, each serving a certain geographical exchange area. Central office locations are often identified in North America as wire centers, designating a facility from which a telephone obtains dial tone.[1] For business and billing purposes, telephony carriers also define rate centers, which in larger cities may be clusters of central offices, to define specified geographical locations for determining distance measurements. In the United States and Canada, the Bell System established in the 1940s a uniform system of identifying each telephone exchange with a three-digit exchange code, or central office code, that was used as a prefix to subscriber telephone numbers. All exchanges within a larger region, typically aggregated by state, were assigned a common area code. With the development of international and transoceanic telephone trunks, especially driven by direct customer dialing, similar efforts of systematic organization of the telephone networks occurred in many countries in the mid-20th century. For corporate or enterprise use, a private telephone exchange is often referred to as a private branch exchange (PBX), when it has connections to the public switched telephone network. A PBX is installed in enterprise facilities, typically collocated with large office spaces or within an organizational campus to serve the local private telephone system and any private leased line circuits. Smaller installations might deploy a PBX or key telephone system in the office of a receptionist. 5. Exchange in Miskolc, Hungary In the era of the electrical telegraph, post offices, railway stations, the more important governmental centers (ministries), stock exchanges, very few nationally distributed newspapers, the largest internationally important corporations and wealthy individuals were the principal users of such telegraphs.[2] Despite the fact that telephone devices existed before the invention of the telephone exchange, their success and economical operation would have been impossible on the same schema and structure of the contemporary telegraph, as prior to the invention of the telephone exchange switchboard, early telephones were hardwired to and communicated with only a single other telephone (such as from an individual's home to the person's business). A telephone exchange is a telephone system located at service centers (central offices) responsible for a small geographic area that provided the switching or interconnection of two or more individual subscriber lines for calls made between them, rather than requiring direct lines between subscriber stations. This made it possible for subscribers to call each other at homes, businesses, or public spaces. These made telephony an available and comfortable communication tool for everyday use, and it gave the impetus for the creation of a whole new industrial sector. One of the first people to build a telephone exchange was Hungarian Tivadar Puskás in 1877 while he was working for Thomas Edison.The first experimental telephone exchange was based on the ideas of Puskás, and it was built by the Bell Telephone Company in Boston in 1877.[7] The world's first commercial telephone exchange opened on November 12, 1877 in Friedrichsberg close to Berlin.[8] George W. Coy designed and built the first commercial US telephone exchange which opened in New Haven, Connecticut in January, 1878. The switchboard was built from "carriage bolts, handles from teapot lids and bustle wire" and could handle two simultaneous conversations.[9] Charles Glidden is also credited with establishing an exchange in Lowell, MA. with 50 subscribers in 1878. In Europe other early telephone exchanges were based in London and Manchester, both of which opened under Bell patents in 1879.[10] Belgium had its first International Bell exchange (in Antwerp) a year later. In 1887 Puskás introduced the multiplex switchboard, that had an epochal significance in the further development of telephone exchange.[11] Later exchanges consisted of one to several hundred plug boards staffed by switchboard operators. Each operator sat in front of a vertical panel containing 6 banks of ¼-inch tip-ring-sleeve (3-conductor) jacks, each of which was the local termination of a subscriber's telephone line. In front of the jack panel lay a horizontal panel containing two rows of patch cords, each pair connected to a cord circuit. When a calling party lifted the receiver, the local loop current lit a signal lamp near the jack.[12] The operator responded by inserting the rear cord (answering cord) into the subscriber's jack and switched her headset into the circuit to ask, "Number, please?" For a local call, the operator inserted the front cord of the pair (ringing cord) into the called party's local jack and started the ringing cycle. For a long distance call, she plugged into a trunk circuit to connect to another operator in another bank of boards or at a remote central office. In 1918, the average time to complete the connection for a long-distance call was 15 minutes. Early manual switchboards required the operator to operate listening keys and ringing keys, but by the late 1910s and 1920s, advances in switchboard technology led to features which allowed the call to be automatically answered immediately as the operator inserted the answering cord, and ringing would automatically begin as soon as the operator inserted the ringing cord into the called party’s jack. The operator would be disconnected from the circuit, allowing her to handle another call, while the caller heard an audible ringback signal, so that that operator would not have to periodically report that she was continuing to ring the line. In the ringdown method, the originating operator called another intermediate operator who would call the called subscriber, or passed it on to another intermediate operator.[14] This chain of intermediate operators could complete the call only if intermediate trunk lines were available between all the centers at the same time. In 1943 when military calls had priority, a cross-country US call might take as long as 2 hours to request and schedule in cities that used manual switchboards for toll calls. On March 10, 1891, Almon Brown Strowger, an undertaker in Kansas City, Missouri, patented the stepping switch, a device which led to the automation of telephone circuit switching. While there were many extensions and adaptations of this initial patent, the one best known consists of 10 levels or banks, each having 10 contacts arranged in a semicircle. When used with a rotary telephone dial, each pair of digits caused the shaft of the central contact "hand" of the stepping switch to first step (ratchet) up one level for each pulse in the first digit and then to swing horizontally in a contact row with one small rotation for each pulse in the next digit. 7. Later stepping switches were arranged in banks, the first stage of which was a linefinder. If one of up to a hundred subscriber lines had the receiver lifted "off hook", a linefinder connected the subscriber's line to a free first selector, which returned the subscriber a dial tone to show that it was ready to receive dialed digits. The subscriber's dial pulsed at about 10 pulses per second, although the speed depended on the standard of the particular telephone administration. 7. IDENTIFY THE AUTHORITIES RESPONSIBLE FOR GENERATION OF POWER The Power Holding Company of Nigeria (abbreviated PHC or PHCN), formerly the National Electric Power Authority (abbreviated NEPA) was an organization governing the use of electricity in Nigeria. The company runs a football team, NEPA Lagos. It represents Nigeria in the West African Power Pool. The history of electricity development in Nigeria can be traced back to the end of the 19th century when the first generating power plant was installed in the city of Lagos in 1898. From then until 1950, the pattern of electricity development was in the form of individual electricity power undertaking scattered all over the towns. Some of the few undertaking were Federal Government bodies under the Public Works Dept, some by the Native Authorities and others by the Municipal Authorities. Electricity Corporation of Nigeria (ECN) By 1950, in order to integrate electricity power development and make it effective, the then-colonial government passed the ECN ordinance No. 15 of 1950. With this ordinance in place, the electricity department and all those undertakings which were controlled came under one body. The ECN and the Niger Dam Authority (NDA) were merged to become the National Electric Power Authority (NEPA) with effect from 1 April 1972. The actual merger did not take place until 6 January 1973 when the first general manager was appointed. Despite the problems faced by NEPA, the authority has played an effective role in the nation's socio-economic development thereby steering Nigeria into a greater industrial society. The success story is a result of careful planning and hard work. The statutory function of the authority is to develop and maintain an efficient co-ordinate and economical system of electricity supply throughout the Federation. The decree further states that the 8. monopoly of all commercial electric supply shall be enjoyed by NEPA to the exclusion of all other organisations. This however, does not prevent privy individuals who wish to buy and run thermal plants for domestic use from doing so. NEPA, from 1989, has since gained another status-that of quasi-commercialization. By this, NEPA has been granted partial autonomy and by implication, it is to feed itself. The total generating capacity of the six major power stations is 3,450 megawatts. In spite of considerable achievements of recent times with regards to its generating capability, additional power plants would need to be committed to cover expected future loads. At present, efforts would be made to complete the on-going power plant projects. Plans are already nearing completion for the extension and reinforcement of the existing transmission system to ensure adequate and reliable power supply to all parts of the country. By 1970, the military government appointed a Canadian Consultant firm "Showment Ltd" to look into the technical details of the merger. The report was submitted to the government in November 1971. By Decree No. 24 the ECN were merged to become the NEPA with effect from 1 April 1972. The actual merger did not take place until 6 January 1973 when the first general manager was appointed. The day-to-day running of the authority is the responsibility of the managing director. In the early 1960s, the Niger Dam Authorities (NDA) and Electricity Corporation amalgamated to form the Electricity Corporation of Nigeria (ECN). Then, immediately after the Nigerian civil war, the management of ECN changed its nomenclature to NEPA. What is currently referred to as the Power Holding Company of Nigeria was formally known as National Electric Power Authority. For several years, despite consistent perceived cash investment by the federal government, power outages have been the standard for the Nigerian populace, however citizens of the country still do not see this as normal. Because of such outages, NEPA has been humorously nicknamed "Never Expect Power Always".[1] Generally, the tariff has been criticised as being too low compared to the cost of generating power. The federal government of Nigeria has 9. increased the tariff to attract foreign investors since 1 July 2010 in order to meet the growing concern for foreign investors into the electricity sector. LOCAL DISTRIBUTION COMPANIES The government has divided the current PHCN distribution sector into separate companies or entities that will be called Local Electric Distribution Companies or Local Distribution Companies (LDC) among the regions. As of April-2014 there are 11 Distribution Companies: • Abuja Distribution Company • Benin Distribution Company • Eko Distribution Company • Enugu Distribution Company • Ibadan Distribution Company • Ikeja Distribution Company • Jos Distribution Company • Kaduna Distribution Company • Kano Distribution Company • Port Harcourt Distribution Company • Yola Distribution Company 8. POWER SUPPLY DESIGN AND DISTRIBUTION I think about system concerns and interactions when designing instrumentation. One issue often overlooked is power regulation and distribution. I discuss some of the concepts involved in designing power systems for instrumentation. At the end of the column, I present a case study for powering a data acquisition system on a submarine. Methodology Early in the development of an instrument, you should consider the power regulation and distribution. Too often, the project team pushes off the design until it is too late. Then you are stuck with trying to "shoe-horn" the power subsystem into a tiny space with little time to do it. The power design affects many things including electromagnetic compliance, weight, size, and heat dissipation. 10. A proper approach considers the instrument as a system with many interacting components and constraints. The power subsystem is just one of the components. Here are the major steps in designing the power regulation and distribution: • Define the source of power and understand its actual condition • Determine the needs and constraints of the system • Understand the types of converters • Select the method of distribution If you use the AC mains for input power in your instrument, you need to know the reliability of service. Many AC lines suffer from dropout, surge, over voltage, spiking, and low voltage. You should filter the input power to survive some of these anomalous conditions. Governmental regulations may require power factor correction and electromagnetic compliance. Moreover, you may want to provide battery backup, such as an uninterruptible power supply, to maintain robust operation. If your power source is DC, such as batteries or solar panels, you have another set of constraints and environmental conditions. As John Witzel points out in this issue of My Favorite Experiment column, batteries require special consideration in charging and discharging. (Honestly, John and I did not collude in preparing our columns!) Power conversion Once you establish the input power, select the type of power regulation and distribution that is most suitable. In general, power supplies have four major components or subsystems: AC-to-DC conversion, filtering, regulator, and output filtering. Figure 1 illustrates the general configuration for power regulation. Distribution of power usually occurs at one of three points in Figure 1, at the front end with AC power, immediately after the AC-to-DC conversion with raw DC power, or after the output filter stage with filtered DC power. 11. Fig. 1. The general configuration for power conversion. (© 1996, Oxford University Press, Inc. Used with permission.) Once you understand the basics of regulation, select the regulator. The types of regulator that can be used are: • Linear regulation where a pass transistor controls voltage and reduces ripple • Switching regulation that uses transistors as switches to generate high frequency modulation • Ferro resonant regulation where a constant voltage transformer controls voltage and reduces ripple The constant voltage transformer in ferro resonant regulation is large and heavy and usually constrains it to ground installations for uninterruptible power supplies. Typically, most applications incorporate either a linear regulator or a switching power supply. Linear converters Linear regulation uses a pass transistor as the control element to remove or reduce ripple in the output DC power. Figure 2 shows the general configuration for a linear power supply. 12. Fig. 2. (a) The general configuration for a linear power converter. It uses a pass transistor as a variable resistor to reduce or remove ripples in the filter output. (b) The regulator, in more detail, that controls the pass transistor. (© 1996, Oxford University Press, Inc. Used with permission.) Linear power supplies are simple and inexpensive. They provide excellent line regulation and transient response to changes in load. They tend, however, to be bulky and heavy because poor efficiency (< 40%) limits their power density (< 0.12 W/cm3 or 2 W/in3). Linear regulation and power supplies fit best in low-power situations that demand very "clean" power. Switching converters Switching regulation generates high frequency modulation to transform the voltage and filter the ripple in the output DC power. Figure 3 shows some general configurations for switching power supplies. 13. Fig. 3. Some general configurations for switching power converters. They use switching transistors to modulate the input to the transformer and output filter to reduce ripples in the filter output. (a) Flyback-mode regulation. (b) Forward-mode regulation. (c) Half-bridge regulation. (d) Full-bridge regulation. (© 1996, Oxford University Press, Inc. Used with permission.) Switching power supplies can have excellent efficiency (> 95%) and high power density (> 6 W/cm3 or 100 W/in3). They can accept wide variation of input voltage (> 100%) and frequency (> 100%) and generally have good line regulation and transient response. They can be very small and light. Switching power supplies tend, however, to be more complex and expensive than linear supplies and power factor correction must be added in many applications. Switching power supplies fit best in situations that require efficient power conversion. 9. IDENTIFY CUNSUMER OF ELECTRICITY  Industrial and commercial consumers As a large energy user you want to reduce overall energy costs, by being more efficient and obtaining the best possible long run price. You can go to a provider who owns both electricity generation and retail companies – and whose goal is to sell their electricity to you at the highest price. Or you can work with Simply Energy – an independent electricity retailer with full Electricity Authority 14. registration and the ability to buy electricity on the wholesale market.We are experienced in designing end to end energy efficiency solutions for large industrial sites, from installing plant and control systems to managing compliance, billing and hedging against the spot position. As we do not own any generation assets ourselves, but have full access to the wholesale generation market, we will recommend and implement the best solution for your business. By working with us, you gain greater insights into the market and experience real value gains. We will only work with you if we can prove that we can achieve measurable benefits over the medium-to-long term. Our clients report greater than 10% savings over the medium term through our wholesale electricity supply solutions. Identifying The Best Purchasing Options We start by assessing your electricity load requirements and risk profile, then consider a range of beneficial structures for the medium-to-long term. These might include: • Becoming your retailer, accessing direct wholesale electricity supply on your behalf • Arranging spot supply and fixed price hedges • Implementing tailor-made supply solutions, including fixed price variable volume tariffs • Buying electricity directly from an independent generator. For example, a generator that uses a sustainable resource, like small scale hydro or wind to generate electricity. If you have a small number of large sites, Direct Market Participation (DMP) could also be an option. This allows you to bypass the retailers and buy electricity directly from the wholesale market. We set you up as a DMP and manage the process to secure the benefits without the management hassle. Regardless of who you buy your electricity from, your security of supply remains the same. Transpower, operator of the national grid, 15. and the local distribution companies continue to be responsible for delivering the electricity to your door. Optimising The Value of Your Resources While Minimizing Costs We can evaluate on-site cogeneration alternatives such as waste heat, gas cogeneration or small scale renewable generation, options which may present further cost saving opportunities. In these cases we have the necessary licences to structure appropriate self-supply arrangements or can provide direct market access for you to sell the electricity. We can also help you to: • Identify, implement and measure energy-related initiatives to help you reduce overall costs and optimise your assets • Understand carbon market implications • Review your network charges and tariffs to ensure you are paying the correct regulated charges. POWER DISTRIBUTION Power may be distributed in several ways. One configuration is the centralized supply that delivers filtered DC power via power conductors and power planes to circuits, sensors, and actuators. Another configuration is the distributed supply that delivers raw, unfiltered DC power to local regulation units. Figure 4 illustrates a centralized supply; Figure 5 shows a distributed supply. Fig. 4. Power distribution from centralized power regulation. (© 1996, Oxford University Press, Inc. Used with permission.) 16. Fig. 5. Power distribution with distributed regulation. (© 1996, Oxford University Press, Inc. Used with permission.) Centralized distribution may use either a linear or switching power supply. Typically, it delivers low voltage, sometimes at moderate amounts of current. It is simple in concept and relies on low-impedance conductors to distribute the current the circuits and components. Centralized distribution is best suited for small, localized systems; these range from small handheld devices and personal computers to 21-slot backplanes in equipment chassis. Distributed systems have multiple points of power conversion. They distribute higher voltages at lower currents, than centralized supplies, to local power converters, which usually are switching power supplies. They do not need heavy, expensive conductors. Distributed systems are best suited for big systems such as large equipment racks, aircraft, and ships. Distributed systems tend to be more robust than centralized supplies because they can isolate failure. If designed carefully, they can be simpler to maintain and repair, as well. "Telecom applications demand high reliability with N+1 redundant power supplies that are hot swappable for fast replacement in the event of a power-supply failure." [1] Table 1 gives a comparison of distributed and centralized supplies. Table 1. Centralized versus distributed power regulation. (© 1996, Oxford University Press, Inc. Used with permission.) 17. Buy vs. build This usually is not even a question - buy the power supply. Only in the extreme situations, where either you are squeezing pennies from the mass-production of thousands or millions of units or the application has incredibly harsh requirements (e.g. a satellite), do you design the power supply. Even then, you should have a specialist, such as a consultant or an applications engineer from a qualified power supply vendor, onboard to help you. A friend of mine, whose company manufactures equipment chassis, has an ongoing headache with power supplies. First, the custom-designed unit failed miserably, then the purchased unit from a reputable vendor demonstrated poor reliability. Only by working with the vendor on each application has he been able to avert problems. Commercial power supplies tend to be more reliable, robust, and smaller than custom designs. The commercial vendors can build on economy of scale in manufacturing and years of experience and 18. expertise to build better supplies. In the telecom example, equipment designers are using commercial supplies, ". . . today's trend is toward plug-in power-supply modules, which are easily accessible and serviceable . . ." [2] In the early 1980s, the U.S. Navy found that power supplies caused a disproportionate number of equipment failures. Most of these were custom-designed supplies. In later years, reliable supplies built to military standards by commercial vendors have greatly reduce the failure rate. This example does not mean that commercial supplies are a panacea, but rather that you should find a reputable source of both power supplies and help to use them. Submarine data acquisition system Years ago, I designed a data acquisition system for an experiment onboard a submarine. It had sensors spread out along the outer hull (Figure 6). [3] The sensors each had high-speed analog circuitry and a high-resolution, analog-to-digital converter (ADC). These circuits needed ripple-free DC power. Furthermore, project management mandated that power distribution to the sensors would be low-voltage DC power. The power supply and distribution required careful consideration during design and manufacturing. Fig. 6. Power distribution for a submarine data acquisition system. (© 1996, Oxford University Press, Inc. Used with permission.) The cables that connected the sensors had a fixed number of conductors. Most of the conductors were devoted to data transmission, leaving only four wires for power supply. The wires were 22-gauge copper, which have considerable resistance (16 W/1000 ft or 52 W/1000 m). For a cable run of 50 m each wire had a resistance of 2.6 W; summing the + and return lines, this resistance totaled 5.2 W. By 19. doubling up the wire pairs, the total resistance was cut in half to 2.6 W. One amp of current passing through the wires would then reduce the voltage by 2.6 V at the sensor. I had to decide between linear and switching regulation in each sensor by considering that the16-bit ADCs had a resolution of 610 microvolts. A linear regulator could achieve this kind of noise floor easily, but, with less than 40 % efficiency, it would more than double both the current and voltage drop in each cable. This would seriously affect the low-voltage DC power supply sourcing the current. Therefore, I chose a switching power module for efficient, local regulation in each sensor to maintain adequate power margins. The tradeoff was that a custom filter had to be added to the output of the switching regulator to reduce noise and ripple. Unfortunately, switching power supplies have nonlinear transfer functions (Figure 7). As current demand varied in each sensor, it changed the voltage drop in the cables. This would change its efficiency, which directly affected power consumption and heat dissipation. Consequently, I had to simulate the various possible operations extensively to estimate sufficient margin for operating the system. Then we had to test the actual hardware for the entire system to verify the results of the simulations. 20. Fig. 7. Efficiency varies with both input voltage and output power. (© 1996, Oxford University Press, Inc. Used with permission.) Fig. 8. Actual, measured power consumption is shown to be a nonlinear function of voltage and current variations within the distributed power system. (© 1996, Oxford University Press, Inc. Used with permission.) The upshot is that whenever you develop a system be sure to conceive, design, and test it carefully. Plan for each of these phases early in development. 21.