The 7061 System Voltmeter contains four printed circuit boards (PCBs) which contain the electronic circuitry. Additional option boards may also be fitted. All inputs to the instrument are converted to a dc voltage level and then transformed into time analog pulse trains on PCB 15. On PCB 13, the analog pulse trains are digitised into discrete, equal length time units, which are counted and passed to the display board, PCB 1, for display. The display provides a numerical indication of the input value measured.