When ring signals arrives, or when the user picks up {TAIL ~ the handpiece} of a telephone set attached to {HEAD ~ the apparatus}, the Ac power supply is started 
When ring signals arrives , or when the user picks up { TAIL ~ the handpiece } of a telephone set attached to { HEAD ~ the apparatus } , the Ac power supply is started
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH