V. Read the following text and use the words given in the box to fill in the blanks. transmitting Although principle began receiving his been time The telegraph and telephone are both wire-based electrical systems, and Alexander Graham Bell's success with the telephone came as a direct result of his attempts to (1) _____________ the telegraph. When he (2) _____________ experimenting with electrical signals, the telegraph had (3)_____________ an established means of communication for some 30 years. (4)_____________a highly successful system, the telegraph was basically limited to (5)_____________ and sending one message at a time. Bell's extensive knowledge of the nature of sound and (6) _____________ understanding of music enabled him to conjecture the possibility of (7) _____________multiple messages over the same wire at the same time. Although the idea of a "multiple telegraph" had been in existence for some (8)_____________, no one had been able to fabricate one - until Bell. His "harmonic telegraph" was based on the (9) _____________ that several notes could be sent simultaneously along the same wire if the notes or signals (10) _____________ in pitch.