ZS series can be used in any type of installation,where different volume from different speaker required.Just select the impedance as per your speaker and connect ZS-640/ZS-440 with amplifier output of the same impedance of speaker such as: if the impedance of speaker is 4ohm,so connect ZS-640/ZS-440)(market amplifier in on the real panal) with amplifiers(com-40hm)and connect speaker (4ohm)with ZS-640/ZS-440 on the real panal market speaker out. it can be used same as above with 8ohm/16ohm,even with 70v/100vline(just keep in  mind the impedance of speaker,you are using).the main feature of ZS series is separate on/off switch with 6/4separate volume selector is ZS-640 and ZS-440 respectively.

ZS series can be used in any type of installation,where different volume from different speaker required.Just select the impedance as per your speaker and connect ZS-640/ZS-440 with amplifier output of the same impedance of speaker such as: if the impedance of speaker is 4ohm,so connect ZS-640/ZS-440)(market amplifier in on the real panal) with amplifiers(com-40hm)and connect speaker (4ohm)with ZS-640/ZS-440 on the real panal market speaker out. it can be used same as above with 8ohm/16ohm,even with 70v/100vline(just keep in  mind the impedance of speaker,you are using).the main feature of ZS series is separate on/off switch with 6/4separate volume selector is ZS-640 and ZS-440 respectively.