Well, the title says it all.
The cable is built around the NEC’s PS7205B-1A SSR, which is with GaAs LED input and optically-coupled dual MOSFET output.
The schematic is simple. The only caution is that the C2 — the capacitor at KEYING side, must be rated at 100V. This is because in TS-830S for example, the keying voltage is around -65V.
I have been using this cable with my Kenwood TS-830S, N1MM+ and UCX Log for about three months with no issues whatsoever, with high RF levels in the shack, because my antenna is a multiband dipole with a transmatch.
The CW keying is stable with no distortion in the sent characters even at high speeds.
The white jumper /JP1 on the schematic/ is for selecting the CW pin from the PC’s COM Port — 4 or 7 /RTS or DTR/.