HP EliteBook 2540P

8 Connector pin assignments
1394
Pin Signal
1 TPB-
2 TPB+
3 TPA-
4 TPA+
Audio-in (microphone)/audio-out (headphone) combo
Pin Signal
1 Audio signal in (microphone) / audio out, left channel
(headphone)
2 Audio signal in (microphone) / audio out, right channel
(headphone)
3 Ground (microphone) / ground (headphone)
ENWW 1394 143