In the context of the MT8870 and Proteus, "35" likely refers to:
Once you have the component, here is a simple test circuit to ensure lib 35 (or your version) works. mt8870 proteus lib 35
If you searched this in 2010, you were likely facing a cascade of failures: In the context of the MT8870 and Proteus,
| Step | Intended Action | Simulator Reality |
| :--- | :--- | :--- |
| 1 | Place MT8870 from library | Error: Unknown part name 'MT8870' |
| 2 | Download "MT8870 Proteus Lib 35.zip" | Contains a .HEX file (for a microcontroller) instead of a .MODEL file. |
| 3 | Find a working model | Requires an SPICE subcircuit. The MT8870 has an internal switched-capacitor filter—brutally slow to simulate in real-time. |
| 4 | Run simulation | Proteus crashes or the tone detection lags 10 seconds behind the virtual button press. | Once you have the component, here is a
The Core Technical Irony: The MT8870 requires precise frequency detection (697 Hz + 1209 Hz = '1'). Proteus’s analog solver, especially in v7.x, was terrible at this. To simulate one keypress, the PC had to calculate hundreds of thousands of charge pump cycles inside the chip. "Lib 35" was often a dummy component—a black box that output random digital values just to make the schematic look complete.
If the component doesn't show up despite copying the files: