Wireless networks allow devices to connect to a network using radio waves instead of wires. They have evolved from early systems using spark gaps and low frequencies to transmit Morse code, to modern systems using digital modulation like QAM for high-speed data transmission. Key developments included Marconi's pioneering radio transmissions in the late 1890s, the first radio broadcast by Fessenden in 1906, the rise of FM broadcasting and its advantages over AM in the mid-20th century, and the transition to digital radio technologies and cellular networks. Signaling systems like SS7 also improved public telephone networks by enabling out-of-band signaling for routing calls.