A significant place in the history of telephony is reserved for Russian engineer V.M. Nagorskiy. In 1898, he invented a telephone with phonic calling, a telefonograph, the induction telegraph and the 'elektrosimfonion'.
The phonic device made by Nagorskiy was a unique design. The microphone was positioned in front of the handset with the distance between them adjustable by regulating the degree of feedback. The handset rests on a cradle, closing the circuit with a secondary shunt transformer coil, which was better than operating directly into the line. Thus, it was ready to receive a 'ringing' call. Calls to a nearby station were accomplished by pressing the call button, triggering a strong sound (call signal). A telephone call was then established by simply removing the handset from the cradle (i.e. answering the phone). Such a simple and reliable phone call was of great interest to designers of military field telephones.
Another interesting invention of V.M. Nagorskiy was the telefonograph - the original sound transmitter (knock device) for sending Morse Code audio signals through telephone lines (the knocking device in telegraphy was simply a telegraph for receiving Morse Code characters by ear and consisted of an electromagnet with a spring-loaded arm). For transmission of telegraph signals, which were customarily performed by a telegraph key to 'enter' the telephone line, Nagorskiy used the so-called microphonic effect. This is positive feedback arising from close proximity to the phone and microphone. Thus, in the main, the operation of the telefonograph was similar to a 'calling' phone.
Nagorskiy exhibited his apparatus with great success at the 1900 World Electrotechnical Exhibition in Paris, where he was awarded a medal. Vyacheslav Nagorskiy took an active role in the practical telephonization of his country. In 1896-97 he set up telephone networks in Peterhof, Strelna, Oranienbaum, etc. In 1899 Nagorskiy introduced Russia's first artificial telephone circuit, connecting St. Petersburg to Peterhof, St. Petersburg to Kronstadt and St. Petersburg to Moscow.