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Some references to grid points in the schematic, to help separate the wood from the trees (see the edges of the schematic):
O8 : "System Reset" includes the 3V battery, diode, C38 etc.
- "Back up" leaves, as an arrow pointing down the page, roughly on the dividing line between O8 and P8
K5 : "Back up" reappears, and feeds to two of the SRAM chips (Vss pins)
- It must also go somewhere else, like an ADC or a microcontroller that has an ADC input, to allow it to be checked by the main CPU.
R10 : IC list, and other parts,
IC20 is an inverter chip (hex inverter, probably similar to 74LS04)
IC6 is a DM74LS14 Hex Inverter with Schmitt Trigger Inputs - used to make a clean transition from high to low, as the capacitor for the reset circuit charges up, when it's turned on (or the orther way, if it's reset).
- Andy