Sony DCR-TRV320 Service Manual page 205

9. Headphone Jack Check
Page 3 Address 5A
Bit Function When bit value = 1 When bit value = 0
2 Headphone jack Headphone jack is used
Using method:
1) Select page: 3, address: 5A.
2) By discriminating the bit value of display data, the state of the
headphone jack can be discriminated.
5-68 E