Circuits and prints to let you use a landline (presumably carbon microphone) telephone as a microphone. More info here.
One directory is for a phantom powered adapter. The other is for one with externally supplied power.
To produce an adapter without modification, print the stl parts from that folder, print and etch the corresponding circut, solder and assemble. The root directory pdf contains a ready to print and mask set of positives for both circuits.
BOMs with suggested component sources follows:
Phantom Power BOM:
- 1 Generic 1/4W resistor of a couple hundred ohms
- 1 22 µF capacitor (ceramic or similar)
- 1 200 µF capacitor (electrolytic)
- 2 Zener diodes (5.1V or there about)
- 1 600:600 transformer with center tap eg. 42TL016-RC
- 1 XLR plug eg. from R connector
- 1 Telephone plug eg. this, though check your local charity shop first.
- 6 M3x16 bolts
- 4 M3X40 bolts
- 10 M3 Nuts
- All 3D printed parts
External Power BOM:
- 1 Generic 1/4W resistor of a couple hundred ohms
- 1 22 µF capacitor (ceramic or similar)
- 1 200 µF capacitor (electrolytic)
- 2 Zener diodes (5.1V or there about)
- 1 600:600 isolation transformer eg. EI14
- 1 Telephone plug eg. this, though check your local charity shop first.
- 4 M3x16 bolts
- 4 M3X40 bolts
- 8 M3 Nuts
- All 3D printed parts