The JST 03SR-3S is the 3-position member of the SR series receptacles, a single-row, 1.00 mm pitch connector designed for discrete wire termination via IDC.
Termination and Wire Prep — IDC on 30 AWG Discrete
The 03SR-3S uses IDC termination for 30 AWG discrete wire — not ribbon cable. This means each conductor is individually pressed into an insulation-displacing slot in the contact, so no stripping or crimping is needed. The trade-off is that the wire gauge is fixed at 30 AWG; the IDC slot geometry won't reliably terminate a heavier or lighter wire. The closed-end feature prevents the wire from pushing through the back of the housing, which is helpful during hand assembly in a harness jig.
Position Count and Series Siblings
At 3 positions, the 03SR-3S is the smallest circuit count in the SR receptacle line. The same housing and pitch are shared with the 2-position 02SR-3S and the 4-position 04SR-3S, so the footprint on the mating header side scales linearly with position count — a 3-position header matches this exactly.