The IC 555 in monostable (one-shot) mode produces a single output pulse of fixed width whenever it receives a trigger. To understand the wiring, recall the internal structure: the 555 contains two comparators, an S-R flip-flop, an output stage, and an open-collector discharge transistor whose collector is brought out at Pin 7. The upper comparator monitors the Threshold (Pin 6) against an internal reference of 2/3 V_cc, while the lower comparator monitors the Trigger (Pin 2) against 1/3 V_cc.

Sequence of operation in the monostable circuit:

1. A negative edge on the Trigger pin sets the flip-flop, drives the output HIGH, and turns the discharge transistor OFF so the timing capacitor is free to charge.
2. The timing capacitor charges toward V_cc through the external resistor R, following the exponential law v_C = V_cc(1 − e^−t/RC).
3. When v_C reaches 2/3 V_cc, the upper comparator fires and resets the flip-flop. This snaps the output LOW and simultaneously turns the discharge transistor ON.

Because Pin 7 is tied directly to Pin 6 (both connected to the top of the timing capacitor), the moment the discharge transistor switches ON it provides a near-zero-resistance path that instantly dumps the capacitor's charge to ground, resetting the circuit and ending the pulse cleanly. The measured pulse width is set by T ≈ 1.1RC.

The choice about instantly discharging the capacitor once the threshold is reached is therefore correct — it is exactly what the shared connection accomplishes. The idea that it prevents the capacitor from ever reaching 2/3 V_cc is wrong, since reaching that level is precisely the event that ends the timing period. Claiming it makes the capacitor charge very slowly is also incorrect, because charging speed is fixed by R and C, not by this connection. Finally, it does not auto-trigger the next pulse; the monostable stays in its stable LOW state until a fresh external trigger arrives.