CDI Ignition makes the spark by discharging a capacitor loaded with high voltage (200 - 450 volt) FROM the ignition coil (negative pulse) by using a SCR (Thyristor).

CDI coils have low impedance and inductance (XL< 1 ohm) and can reach high RPM. This type of ignition makes high power and short sparks.

TCI Ignition charges the coil with a current before the spark is done. Spark is done when the current is cut suddenly.

TCI coils have high impedance (>1 ohm) and can reach lower RPM. Spark duration may be longer.