the telephone receiver to his cars. He then adjusts his receiving circuits for various wave lengths and, if he hears no signals, he assumes that no one else is sending within his radius. He therefore “throws in” the transmitting apparatus, which action automatically disconnects the receiving side. He then sends the letters which constitute the “call” of the station desired, signing the letters designating his own station, after sending the call several times. He then listens in again, and if the operator at the desired station has heard his call, the latter answers, and regular telegraphic communication ensues.
Some wireless systems are so arranged that no switching is necessary. The operators can “break” one another, by keeping the telephone receivers over their ears all the time. If the receiving operator should wish to correct the sender, he does so by pressing his key; this is heard by the sending operator when his key is in normal position.
Tuning not only increases the radius of operation, but maintains secrecy as well. By means of careful tuning, two distant stations may be sending simultaneously, and if they employ different wave lengths, the operator at the receiving station may, by adjusting his apparatus to the wave length of the station with which he desires to communicate, “tune out” the other message, receiving only the one desired.
However, if the stations above referred to be quite