2. Major Connector Categories

Scope your search by category before diving into specific families. Each category optimizes for different axes.

Category	Typical use	Rugged / professional examples	Less suitable when
Circular	External harnesses, sensors, payloads, field I/O	MIL-DTL-38999, MIL-DTL-26482, M12, M8	You need dense rectangular modularity or DIN-rail service
Rectangular	Industrial machines, panels, removable modules	Industrial rectangular / Han-style, D-sub, Micro-D	You need cylindrical sealing or compact cable routing
Board-to-board	PCB stacking, mezzanine, backplanes	Samtec, TE, Molex high-speed mezzanine	Vibration exists without mechanical support
Board-to-wire	Internal PCB harnessing	Molex Micro-Fit / Mini-Fit / Nano-Fit, TE, Harwin, JST (various)	External rugged interface unless sealed / latched / potted
Wire-to-wire	Internal splices, replaceable assemblies	Molex sealed families, TE/Deutsch, Amphenol AT/ATP	High-service external panel connection unless designed for it
RF / coax	Antennas, GPS, radios, radar, video, test	SMA, TNC, N-Type, BNC, SMP/SMPM, MCX	Ordinary discrete wiring / uncontrolled impedance
High-current power	Motors, batteries, heaters, PDUs	Anderson SB, Amphenol/TE high-current, 38999 power inserts, Han-style power	Mixed low-level signals without isolation planning
Fiber / data	Long-distance data, EMI immunity, bandwidth	LC, ST, expanded-beam rugged fiber, M12 Ethernet	Dirty field environments without cleaning discipline
Hybrid	Power + signal + data + coax/fiber/fluid in one	38999 hybrid inserts, Han-Modular	Simple low-cost harnesses where separate connectors are cleaner

Often overlooked

Board-to-wire connectors like Molex Micro-Fit, Mini-Fit, Mega-Fit, and sealed Squba are not "hobby" parts. Professional versions have positive latches, polarization, secondary locks (TPA), defined current/voltage ratings, and sealed variants. The dividing line is the specific family and rating, not the brand.

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