mp3 with LineIn

具有LineIn的 mp3 player(撥放器)
可能有LineIn的錄音功能
也可能只有 LineIn 的放音功能(作為LineIn 音源的喇叭)　

即使該mp3 player具有所謂的錄音功能　
可能也只能從麥克風錄音　無法從LineIn錄音？

Some mp3 players/recorders may only record sound from the microphone
even if they have the so called LineIn hole,
i.e. the LineIn only transmits the sound source to amplifier/speaker
but does not record it?