Asus Transformer Pad 300T English User manual
Page 8
... Input Combo Jack The stereo combo jack (3.5mm) connects the ASUS Transformer Pad's audio out signal to your ASUS Transformer Pad and charge the internal battery pack. To prevent damage to amplified speakers or headphones. For microphone input function, the jack best supports headset microphones by ASUS. 8 ASUS Transformer Pad Manual 7 SIM Card Slot (on TF300TG/ TF300TL) Insert a 3G SIM/LTE card into this slot.
... Input Combo Jack The stereo combo jack (3.5mm) connects the ASUS Transformer Pad's audio out signal to your ASUS Transformer Pad and charge the internal battery pack. To prevent damage to amplified speakers or headphones. For microphone input function, the jack best supports headset microphones by ASUS. 8 ASUS Transformer Pad Manual 7 SIM Card Slot (on TF300TG/ TF300TL) Insert a 3G SIM/LTE card into this slot.