The AC adapter supplies +9.5VDC to the printer. The Nickel-cadmium battery
Pack supplies 6VDC.
Here is a brief explanation of how the two power sources interact:
When the DC plug of the AC adapter is plugged into the printer, the unit
will switch from the Ni-Cad battery to the AC adapter. The DC input, after
passing through a 0.4A fuse and a noise filter, is checked for voltage by
the A/D converter to judge whether the input is from the 9.5VDC or 6VDC
Ni-Cad. If the Ni-Cad only is being used, the 'low battery sensing
function' and 'auto power off' functions are activited. When the Ni-Cad
pack is being charged, the A/D converter is used to check that DC is being
inputted from the AC adapter and to activate the 'auto charge off
function'.