Deposits are a loan from the customer to the banker. The terms of that loan are the terms of the ‘account’. We refer to ‘an account’ because the amount deposited is subject to change, and there is a continuous accounting of it as transactions occur so as to show the amount currently on deposit. The terms of the loan are theoretically subject to negotiation between the parties. In practice, they are imposed by the bank. Thus, the number of kinds – the ‘types’ – of accounts available to customers is generally limited, but terms do vary.

Chapter 6 is the third of three chapters laying a basic foundation in German law and politics. The chapter describes the system of German legal education, which aims to develop Einheitsjuristen (a complete of full jurist). The chapter then presents the basics of German (private law) legal methodology. Finally, the chapter considers the expectations and mythology of German legal actors (judges and lawyers) by considering the standards used to exclude some former East German judges and lawyers from the legal profession (in a lustration process) after reunification.

In recent times, banks, financial organisations and technology companies have leveraged emerging technologies such as artificial intelligence, big data and blockchain to transform the global financial market at an unparalleled pace. The term ‘Fintech’, a blend of ‘financial’ and ‘technology’, has become a part of common vocabulary. Generally speaking, ‘Fintech’ refers to the application of technology in providing financial services. The Financial Stability Board (FSB) describes Fintech as ‘technologically enabled innovation in financial services that could result in new business models, applications, processes or products with an associated material effect on financial markets and institutions and the provision of financial services’.

Having examined cheques and bills of exchange in Chapter 8, we now move onto more contemporary methods of payment. In this chapter, we introduce the regulatory framework and basic concepts, and then discuss the ePayments Code. We then consider two sets of emerging issues: Open Banking and Central Bank Digital Currency.

Chapter 3 challenges the tradition in comparative legal studies, which treats Germany exclusively as a representative of the Civil Law family. Through excerpts of leading German legal theorists of the twentieth century, the chapter demonstrates that there has always been resistance to the Civil Law orthodoxy in the German legal culture. This includes a survey of the Free Law Movement (Kantorowicz), the Pure Theory of Law (Kelsen), and the Radbruch Formula (Radbruch). The chapter concludes with a discussion of the Federal Constitutional Court’s Lüth Case, in which the Court announced the Basic Law’s “objective order of values.”

In the last few chapters we have examined the propagation of electromagnetic waves; freely propagating waves in Chapter 8, waves guided along transmission lines in Chapter 9, and waves guided within waveguides in Chapter 10. But we paid no attention in these discussions to the generation of these waves. In this chapter our goal is to remedy this shortcoming. As we will show, an oscillating current in an open-ended wire can produce an electromagnetic wave. We will examine the distribution of the radiated power, the total radiated power, the efficiency of the power generation, the polarization of the wave, and the input impedance of a few simple radiating systems. We will start by examining a short, or elemental, dipole antenna, and then expand this to longer, more efficient, antennas. We will also look at the field distribution and power density produced by an array of antennas, and show how the distribution varies with the relative phase of the radiators.

We have now reached the end of our journey exploring the fundamentals and simple applications of electromagnetics. We are surrounded by applications of these concepts in our daily lives. A partial list includes electric motors and generators, microwave ovens, remote controls for our television or garage door opener, magnetic resonance imaging, broadcast, satellite, or cable television, high-speed chip-to-chip communications on printed circuits, and many, many more. While we have not dealt much here with the specific engineering principles of many of these devices, we have tried to lay the fundamental concepts on which they are based.

To this point in our discussions, we have dealt solely with static fields. We started with static electric fields, in which all charges are stationary. The electric fields produced by these charges are stationary as well. With electric fields, we developed the notion of the electric potential, the energy stored by electric fields, and the capacitance of a configuration of conductors. We then moved on to introduce static magnetic fields, which are produced by stationary currents. For magnetic fields, we have also introduced potential functions, one a vector function, the other a scalar, but we have not yet discussed the energy stored by a magnetic field, or the inductance of a configuration of current-carrying wires. We will, of course, treat these important topics, but before we do so, we find it useful to take a first look at some time-varying effects. In particular, we will develop a law known as Faraday’s Law, which is the basis for circuit elements such as inductors and transformers, as well as electrical generators and many other useful devices. After we have mastered Faraday’s Law, we will be in a much better position to discuss the energy stored in magnetic fields and inductances, and so we will return to these topics at that time.

Having examined many useful and interesting properties of first static electric fields, then static magnetic fields, and most recently the combination of electric and magnetic fields through the introduction of time-varying effects, we have reached a turning point in our studies. Specifically, we will introduce what is perhaps the most revolutionary concept in electromagnetism: propagation of electromagnetic waves. Electromagnetic waves can carry information and energy, and their properties are described in full using Maxwell’s Equations. We will explore these properties in detail in this and the following chapters.

In the previous chapter we introduced transmission lines, structures consisting of a pair of conductors that guide a high-frequency electromagnetic wave in the space between the conductors from a source to a load. We considered a number of different geometries (parallel plate, twin-lead, co-axial), each with a uniform cross-section, that guide the wave in the $\pm z$-direction, and we discussed the properties of signals carried by the transmission lines, largely in terms of the potential difference $\tilde{V}\left(z\right)$ between the conductors and the current $\tilde{I}\left(z\right)$ flowing in one conductor and returning in the other. For many high-power, high-frequency applications, waveguides are often used to guide electromagnetic waves from source to load. Unlike a transmission line, a waveguide typically consists only of a single conductor, which is hollow, with the wave existing in the interior of the waveguide. Waveguides are often used for frequencies ranging from 10 to 100 GHz, and suffer lower losses in this range than do transmission lines. The typical transverse dimension of a waveguide is a few centimeters, on the order of the wavelength of the wave inside. A few examples of waveguides are illustrated in Fig. 10.1. The parallel plate waveguide shown in Fig. 10.1(a) is not in common usage, but serves as a simple geometry for developing the properties of general waveguides. (Parallel plates differ from most other waveguides, in that they consist of two conductors and can function as transmission lines or waveguides.) Also shown in this figure are (b) rectangular and (c) circular waveguides. While the electromagnetic principles for the circular waveguide are similar to those of the rectangular waveguide, the mathematical functions needed for this geometry are not familiar to most undergraduate students, so we’ll need to introduce these functions. Also, while we devote our attention here to conducting waveguides, be aware that dielectric waveguides, such as optical fibers and photonic crystals can be treated in a similar manner. With the exception of TechNotes 10.1 and 10.2, we will not consider dielectric waveguides in this text. Optical fibers are common conduits for optical signals, and find application in medical instruments and communications systems.