This small research is dedicated to the evolution of the shape of a telephone set. We are focused on a telephone set not as a system for transmitting and receiving voice information but on a telephone set as a final element of the entire process, which is in direct contact with a user.
Therefore, the principle of operation of a telephone set will only be of interest for us insofar as technological innovations affected its shape. Nevertheless, a short excursion into the history of the subject will not be redundant.

The principle of operation of the telephone was developed in 1784 but an operating telephone set only appeared in 1876 and the patent for it was issued to Alexander Bell. Initially, the new invention did not enjoy popularity. Serious businessmen did not want to invest in a "useless toy". To raise money for further research, Bell organized then-unusual shows - a box with a loud-speaker was arranged on a scene and an assistant played the organ in another house (later in another town). A delighted audience listened to the music enthusiastically. It was not the sound quality that excited general admiration, but the technical miracle that allowed transmitting any sounds for large distances.
A bit later, the invention was perfected by Edison who made possible sound transmission for considerable distances. Telephone lines with a switchboard as a communication center connected telephone sets. Initially, the switchboard operated exclusively with the participation of a man: a subscriber called a "hello-girl" who connected him to another subscriber, so there was no need for a device for dialing the number of a desired subscriber. Then dial exchanges appeared and there emerged a necessity of equipping the telephone set with a dialing device. A number was dialed by rotating a disc and then by using a keyboard. The next significant step in the telephone evolution was use of wireless communication, which allowed using one and the same number and apparatus at any point of the world.

Receiver
The first user telephone set comprised two horns with membranes, the wires from which were hidden in an undistinguished box. One horn was designed for a user to speak into and the other one was applied to an ear for listening. Both hands were busy which was not considered as a serious disadvantage at those times because first telephone calls were so exciting that the process was self-sufficient.

It was not long until the telephone became an ordinary and even trivial object of everyday life designed not only for pleasure but also for useful work. There emerged a necessity to free at least one hand for performing some operations (for instance, for writing down a telephone message) simultaneously with speaking.
The problem was approached in two ways. The first solution was not a success. The transmitting horn was built in the telephone casing and a user only had to hold a receiving horn in his hand. As a result, one hand became free, but the user's mobility was limited.

The second approach was more promising. Both horns were connected to a common handle so that a user could hold them with one hand. This is how the first telephone receiver - two horns attached perpendicular to a handle - appeared.

With time the horn size was matched with the head shape - the horn contacting the ear became short and the transmitting horn became long and curved.

Later, plastic began to be used for manufacturing the telephone casing, which immediately created ample opportunities as regards the casing shape. However, the inertia of thought which acts as the main brake on progress resulted in that the telephone set preserved its traditional shape for may decades. Designers only allowed a slight styling. The receiver shape became smoothed and the possibility to make the handle curved (matched with the round shape of the head) led back to symmetry.

Only in the fifties, designers ventured to give the receiver the form that had nothing in common with horns and the receiving and transmitting microphones were placed directly in the handle. The technology had long ago reached the level at which that arrangement became possible and ergonomics just required that the receiver be made lighter in weight and more convenient for the ear and the hand. Inertia locks opened and a flow of fresh designers' solutions, including most extraordinary ones, invaded the telephone industry.
For example, in Ericofon model of 1956, the telephone set and the receiver make an organic whole. When you want to dial a number, it is no use applying the receiver to the ear, and when you are speaking, a dialer is also useless. Today, a telephone set consisting of a receiver only is a normal thing but at the end of the fifties it was a revolutionary breakthrough.

Control board
The evolution of a control board also led to the appearance of a dial-in-handset telephone. The most frequently used functions are switching on/off and ringing to a subscriber.

First telephone sets did not require any special device for ringing to a subscriber. It was enough to tell a "hello-girl" the name of a needed subscriber.

However, the growing number of telephones and the invention of an automatic telephone exchange resulted in that the function of ringing to a subscriber was shifted to a user.
Initially, the number indicator was similar to a scale plate of a measuring device and was controlled by means of a handle with a pointer that pointed to a specific figure. The handle was inconvenient to rotate. The process was time-consuming.

Subsequent efforts resulted in inventing a dialer that could be easily rotated with a single finger. As distinct from a pointer that had to be exactly matched with a required figure, no such precision was needed because it was enough to put a finger in a required hole.

The keyboard has many advantages over the dialer. First, the keyboard has been used for a variety of devices so far, consequently, it is familiar and universal. Second, a telephone number can be dialed very quickly without waiting for the dialer to return to the initial position. Third, motor memory allows remembering the finger arrangement while dialing a number and subsequently dialing frequently used numbers almost automatically.

And, in addition, the keyboard allowed minimizing the telephone size, which provided a resource for trimming the telephone set so that only one element - a receiver - remained. Previously, the telephone size was determined to a considerable degree by the dialer size. The keyboard removes this limitation.

Invention of wireless communication is a significant step among great and small revolutions in the telephone history. It allowed using one and the same telephone number and apparatus initially everywhere within a city and then within a country. Now it is possible practically everywhere in the world.

How have wireless communication technologies affected the telephone shape? Communication technologies have had but a minor effect whereas new use conditions and manufacturing technologies have exerted a strong influence on it. A stationary telephone may be of any reasonable size while a mobile telephone set had to be made compact and light-weight. As a result all technical "stuffing" moved into the receiver (i.e., the body was trimmed) since the available technologies allowed fabrication of miniature microcircuits. The receiver size is reduced to an acceptable minimum so that the receiver is convenient to hold in a hand and difficult to lose in a pocket or bag.

At this stage, it is necessary to resolve the following contradiction. The telephone must be small when stored and must increase in size when used. As a result, the telephone became dynamized. It was separated into two, three parts having a hinged joint.
For instance, there are telephones-bracelets.

It is also desirable to protect the telephone keyboard from damage or contamination. As a result, various designs of a cover appeared (which is a less ideal solution).

In other versions, dynamized telephone parts were joined in a non-operating state so as to cover the keyboard (in that case, there are no additional low-functionality elements because minimum necessary elements perform an additional function themselves, consequently, the system is more ideal).

The following step was the appearance of a telephone in a single-piece elastic shell. It is moisture and shock resistant.

The new conditions of using the telephone, for instance, while driving a car, required that the telephone be free of a receiver at all, or better to say, be free of a hand-held receiver. As a result, only an ear-piece, attached to a head, and a microphone remained. Theoretically, the number-dialing function must be performed by voice because adding one more keyboard to this construction would be a step back as regards the functional convenience. (Many telephone models provide possibility to call a subscriber without dialing a number but just by saying the subscriber's name. Isn't it a return to the "hello-girl" but on a new - virtual - development volute?)

Probably, some time will elapse and we will start carrying the telephone directly in the ear. Then the telephone shape as an aesthetic and ergonomic object will cease to be of any importance.
Recently, information has appeared about the invention of a miniature telephone implanted in a tooth. The "dental telephone" comprises a miniature microphone and a radio wave receiver. Sound in the form of a digital radio signal enters the receiver and is transmitted to the inner ear due to the good sound conductivity of bones.