What is this type of headphone icon in notification bar? My phone (LG G3) shows two different types of headphone icons. They are the leftmost icons in the images below. The first is a normal headphone icon. What is the second one?

I think it might be USB headphone, but that doesn't make sense, because I don't have USB headphones and never use USB headphones with the device.

I have noticed sometimes when I use the aux cable for my car, it displays the second icon instead of the first one. It shows the first icon whether I use headphones with a built-in mic or headphones that don't have a mic - it's the same icon.

Image 1: normal headphone icon



Image 2: ??



Any thoughts?

Edited images to make them smaller
Second one is showing a line out or auxiliary audio
 icon, which means that it had recognised that a jack had been plugged in ( but it doesn't detect a speaker or maybe it detects the speaker ) but fundamentally to differentiate  between  regular headset (with or  without mic) and speaker connected with line out

If this happens when you connect to regular headphone, it indicates some dirt or pocket flint , preventing recognition of head phone. Cleaning with a tooth pick , ear bud and blowing air to dislodge muck should fix. If it doesn't, try app mentioned here 
What is this icon in my status bar?

Later versions of LG also differentiate between headphone with speaker and without speaker

I had this icon show up on a Dopod phone, owned a decade ago