This week on telepholution focuses on awesome results of the combination of acoustic string techniques with telegraphy. The results marked the beginning of unending discoveries and inventions of technologies in communications.

Human inquisitiveness knows no bound. The continuous yearning to know how things work, the resultant effects of occurrences and the reasons why some things are meant to be or not, is the major characteristic of the average human. Thus, it was not unexpected to have Innocenzo Manzetti (1844) conceive the idea of importing some techniques of the acoustic string phone into telegraphy. The idea aimed at transmitting voices (as in the acoustic phones) whilst employing the use of electromagnetic signals via the telegraph lines as against the use of conventional strings in acoustic phones. Hence, the birth of ACOUSTIC TELEGRAPHY. Although conceived this idea, Manzetti never pursued it further.

In a bid to improve the EM telegraph which was limited to only textual messages and transmission of one message at a time, Manzetti's idea was revisited years after by various scientists including Alexander Graham Bell, Elisha Gray and Thomas Edison. Acoustic telegraphy was based on multiplexing telegraph messages by assigning different audio frequencies to each message and then transmitting over a single telegraph line. The concept of acoustic telegraphy is very similar to the modern frequency division multiple access (FDMA) technique, whereby voices or other signals to be transmitted and multiplexed, allotted certain frequencies and then modulated with a carrier signal in order to avail the signals to reach the intended destination. It is then appropriate to infer that with the advent of acoustic telegraphy came the concept of MODULATION. The improvement of the EM telegraph with the aid of acoustic telegraphy led to the conception of a device which significantly reduced cost of telegraph services and allowed voice transmission over telegraph lines. This device was called the SPEAKING TELEGRAPH, also known as a TELEPHONE. Various scientists are being owed the credits of inventing the telephone but, Alexander Graham Bell is often regarded as the inventor and father of telephone. This resulted from the fact that his invention was first patented and also, had a model that was commercially viable.

Bell's telephone comprised of the transmitter, telegraph line and the receiver. The transmitter; a funnel shaped membrane had a double electromagnet on a ring with a soft iron placed in its centre. A mouthpiece which is attached to the membrane, directs spoken voices to the centre of the membrane causing it to vibrate and the soft iron induces corresponding currents in the coils of the electromagnet. The voice vibrations along with the induced currents travel down the telegraph line to the receiver which also consists of an electromagnet with a disc of soft iron placed closed to it. At reception, the voices modulated with current flow through the electromagnet, causing the disc to vibrate and creating sound waves in air which can be heard. The disc vibrations are proportional to the intensity of current through the electromagnet.

Other scientists contributing to the invention of the telephone are Elisha Gray (1876) and Thomas Edison (1878) with the liquid transmitter and carbon grain transmitter respectively. Gray's design was never pursued further whilst Edison's served as one of many improvements to the Bell's model. Bell telephone had it first commercial usage in August 1876 and covered a distance of 10 miles (16 km). With the aid of numerous improvements from other scientists, the operating range improved significantly. These improvements would be the next topic of discourse in the series. Be sure to keep it a date for the next episode....thanks for the view!
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