Why does this cable not work with my video camera or digital audio recorder?

Smartphones use the headphone jack for both audio output and input.  In order to do this, a fourth pole was added to the standard 3.5mm connector.  However, long before the advent of smartphones, digital audio recorders were using the standard 3-pole 3.5mm connector.  

Pole comparison


Nflightcam Cockpit Kit for Smartphones - Helicopter


Nflightcam Cockpit Kit for Smartphones - Twin Plug


NFlightcam Smartphone Audio Cable Twin Plug SKU 409


NFlightcam Smartphone Audio Cable Helicopter