balanced/unbal.; optoswitch... ajutor va rog

Salut am citeva nelamuriri.

1. Opto Switcher - am inteles, cred, ce e asta si cum face decuplarea:
"allows remote switching of mains powered equipment while maintaining electrical isolation fron the mains. Switching occurs at the zero crossing point of the mains cycle, which together with spike suppresion components, ensures that interference is virtually eliminated"

nu pricep ce utilizare practica are intr-un sistem audio.
este cumva pur si simplu un comutator care nu produce paraziti la inchidere/deschidere? cit de importanti sunt acesti paraziti?

2. intrari/iesiri 'balanced/unbalanced'

zice asa intr-un manual:
"Matchpack Pro Bi- directional Stereo Interface Unit:
Interfacing unbalanced semi- pro equipment to professional balanced line levels.
• Fitted with 4 XLRs for balanced and 4 phono sockets for unbalanced connections.
• Multi- turn gain presets are provided, accessible through the front panel.
• Supplied set for a nominal 14dB attenuation between line and the equipment."

la fel, inteleg ce zice asta ca face, dar nu inteleg ce s-ar intimpla daca leg, de ex,  o iesire balanced de la un echipament "pro" la o intrare "unbalanced", a PC-ului de exemplu.

cum pot sa stiu daca o intrare/iesire este sigur balanced sau unbalanced?
este periculos sa le amestec fara o interfata ca si cea de mai sus?

Multumesc