The "Nextel Sonido" (or the "Chirp") was the signature audio alert for Nextel's service, becoming a massive cultural icon in the early 2000s. It signaled an incoming direct radio transmission, allowing users to communicate instantly without using their monthly cellular minutes. The Technology: iDEN and the "Chirp"

: Following the Sprint-Nextel merger in 2005, the aging iDEN network faced interference issues (often referred to as "rebanding") and was eventually decommissioned in 2013 to make way for LTE.

: While the physical Nextel network is gone, the "Direct Connect" concept survives through apps like Zello or the built-in Walkie-Talkie feature on Apple Watch .