Canon multipass c3000 Service Manual (en)

5.5.5 Lightning protection
The fax unit’s electrical components are protected from abnormal voltage caused by
Protected Component 
Safety Device
SCNT board assembly
Arrestors (ZD2) on the primary side of the SCNT board NCU 
discharges a voltage over 320 to 480 VDC via the power cord
When protection is not possible
The SCNT board may not be adequately protected even with the protection
circuits if lightning strikes the telephone line.
5.5.6 Power leakage protection
The AC line, telephone line, and metal parts of the fax unit are completely insulated.  The
fax unit has a grounded power cord (three-prong plug) to prevent electrical shock.  If power
leakage does occur, use the fax unit only with a grounded electrical outlet supplying the
proper voltage.
Chapter 1: General Description