BSS Audio FDS-310 Owner's Manual - Manual (Page 25)

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19.0 Polarity switching and Output Polarity
reversal option
Each frequency bands' control surface includes a POLARITY switch (See
Figure 6.1). Depressing it reverses the polarity ('phasing') of the signal
emerging from the related output socket. It is a valuable 'instant'
troubleshooting aid in complex multi-driver installations.
Polarity in/out relations are factory set, so at any input and any related output:
• XLR + or HOT goes to Pin 3.
• Phone sockets + or HOT goes to tip.
Although wired to 'Pin 3 HOT' convention, this arrangement is perfectly
compatible with XLR Pin 2 systems (to IEC 268 standard), provided input and
output are wired alike (meaning 'Pin for Pin'). This applies to the phone plugs
only. The only problem with operating in 'Pin 2 HOT' mode concerns the
phone plugs, where the 'ring' terminal become the 'HOT' one. If the
remainder of the system is wired 'Pin 2 HOT', you may wish to reverse the
sockets polarity, so the tip becomes the 'HOT' terminal. Refer to section 22.5
for information on reversing polarity.
Aside from loudspeaker drive-unit connections, polarity transposition can arise
in balanced interconnections, if 'HOT' and 'COLD' are swopped on one
(stereo) channel, but not the other. If this has happened, it is more likely to
occur before the crossover. The low frequencies will sound weak and the
stereo image will be thin and distant. If you set up sound reinforcement
systems frequently, a 'phase' or 'polarity' checker set is an invaluable tool for
speedily tracking down any mistakes, and confirming that inter-channel and
inter-band polarity are all correct.
POLARITY switch