This cable allows you to record all ATC and cockpit intercom transmissions on a digital audio recording device. Unlike a smartphone, this cable uses the standard 3-pole audio input and is compatible with most digital audio recorders, digital video cameras, DSLR cameras with audio input, and other standard audio recording devices.
Why does this cable not work with my smartphone? Long before the advent of smartphones, digital audio recorders were using the standard 3-pole 3.5mm connector. Smartphones have a 4th pole added to the standard 3.5mm connector, allowing the headphone jack to be used for both audio output and input.