Philips HDRW720 Service Manual page 157

Circuit-, IC descriptions and list of abbreviations HDRW720/0x, DVDR725H/0x 9. EN 157
("D_IKLL"-line) or the "IPFAIL"-signal from power-supply-unit
(in this case it's the combination of "A_KILL" and "IPFAIL").
In addition to that the DAC [7001] and the cinch outputs can be
killed (muted) in case of "digital silence" by the circuit around
[7008], [7009] and [7010], when no audio data are available
(e.g. "D_DATA0"-line zero).
This function can be also activated via the "ION"-line (set to
high during any stand-by mode). To avoid signal distortions
(clipping) the mute transistors for cinch rear out [7415], [7416]
are decoupled via [7011].