Plug or receptacle?
A plug illustration does not show the inside of its receptacle. The label describes this sketch, not every component with the same family name. An unclassified role stays explicitly unclassified.
Observation guide
What can you safely use to narrow a connector?
Use repeatable physical observations to reduce the candidate set. This guide describes atlas filters, not a universal connector taxonomy and not permission to mate hardware.
Reading an illustration
Start with the view. Then the clue.
A connector name is not a drawing orientation. These original schematics separate what is depicted from what the exact product still needs to establish.
Cable-end plug
Mating-face outline. Looking toward the plug opening; not the wire or solder side.
USB Type-C →
Plug illustration
Exterior side view. Tip is drawn to the right. This is a side view of a plug, not the inside of a socket.
3.5 mm TRS connector →
Plug-style exterior
Exterior side view. Cable side is at the left. This is an exterior view; no optical end-face or electrical contact array is depicted.
FC fiber connector →Front, rear or side?
Do not turn an exterior or unnumbered face sketch into a solder-side, board-side or mirrored pin assignment. The engineering reference declares its own source view separately.
Illustration or measurement?
All recognition artwork is not to scale. Equal boxes do not show relative size. Nominal contact counts come from written evidence, not dots counted in a drawing.
Never use trial fitting or an optical end-face inspection to settle an uncertain identity. Stop with an unresolved candidate and consult exact-product documentation.
Know what the drawing can show
Outline, pattern or just a label?
Some older artwork uses a generic symbol. Enlarging it cannot reveal details that were never drawn. These three examples explain where to stop and read the written reference.
Module-face schematic
The mounting hole and contact edge orient this illustration only; no underside, socket opening or approved installation direction is shown.
The simplified edge fingers and gap are not a verified key pattern.
M.2 card edge interface →
Front-oriented modular sketch
The latch-like projection is drawn at the bottom. It does not settle plug/receptacle role or the view used for wire numbering.
Filled versus unfilled marks illustrate population, not wire order.
6P4C modular plug (often sold as RJ11) →
Generic family symbol
Label-led symbol — not interface geometry. Read the exact designation and written reference; do not identify a physical connector by this generic shape.
This symbol has no declared front, rear or installation view. Use the written reference and exact drive/backplane documentation.
The dot count is not the documented contact count.
SATA 15-pin power connector →Four of 14 inherited label-led records now have separate, original keyed-slot studies; ten are unresolved. Their inherited SVGs remain unchanged.
More useful places to look twice.
P002 / P003
USB Type-B: shorter or taller?
Compare the clues →P005 / P006Mini-B or Micro-B?
Compare the clues →P006 / P007One Micro-B section or two?
Compare the clues →P008 / P011HDMI or DisplayPort?
Compare the clues →P009 / P010Mini HDMI or Micro HDMI?
Compare the clues →P013 / P014 / P015DVI: the grid and the blade
Compare the clues →P019 / P020TRS or TRRS plug?
Compare the clues →P066 / P067LC or SC exterior?
Compare the clues →P203 / P124FC or ST exterior?
Compare the clues →P027 / P231 / P205BNC, Mini-BNC or HD-BNC?
Compare the clues →P061 / P062SD or microSD card outline?
Compare the clues →P119 / P120CompactFlash or CFast label?
Compare the clues →P121 / P122CFexpress: read Type A or B
Compare the clues →P123 / P122XQD or CFexpress Type B?
Compare the clues →P030 / P298M.2 or Mini PCIe / mSATA?
Compare the clues →P029 / P118Internal SATA or eSATA?
Compare the clues →P029 / P194SATA data or power reference?
Compare the clues →P195 / P199Slimline or Micro SATA label?
Compare the clues →P196 / P194SAS or SATA drive-side reference?
Compare the clues →P295 / P296 / P297PCIe: read the mechanical-form label
Compare the clues →P105 / P106 / P107FireWire: compare the named forms
Compare the clues →P108 / P109Mini-DIN: look beyond the circle
Compare the clues →P111 / P112 / P113Telephone: positions versus contacts
Compare the clues →53 illustrations have explicit view/role annotations (24 inherited + 29 added in V86). This internal audit is not independent artwork review; other forms keep their original evidence and unresolved views.
Bayonet / twist coupling
Look for a push-and-twist style coupling or bayonet retention explicitly documented in the recognition tags.
3 tagged formsThreaded coupling
Look for a screw-threaded coupling explicitly normalized in the recognition tags.
5 tagged formsPush-pull coupling
Look for a push-pull shell or release mechanism explicitly documented for the form.
3 tagged formsSnap-on coupling
Look for a snap-on RF-style coupling documented for the form.
12 tagged formsLocking / latching shell
Look for an explicit locking, latching or twist-lock retention feature.
4 tagged formsExposed card edge / slot
Look for exposed edge contacts or a card/slot interface rather than a conventional plug shell.
Shape is useful, but it is not identity.
The atlas currently exposes 34 normalized shape labels. Use an exact shape only when it is genuinely visible; broad outline is safer when you are unsure.
asymmetric shellbayonetbladebottom contact fpccard edgechamferedd subdual rowhistorical miniinlineinternal headerkeyedkeyed power housingled headerlow profilemagnetic contact stripminiature crimp housingminiature rf snapmodularopticalovalrectangularribbonroundrow headershrouded single rowslotsplitsquarestackedtabtop contact fpctrapezoidtwo row header
Contact count needs a convention.
146 forms have a normalized nominal contact count and 69 remain unknown; 11 optical forms use not applicable for electrical contacts. A housing position count, populated-contact count, optical-fiber count and blade convention are not interchangeable. Keep unknowns visible when you are not certain what is being counted.
Use comparisons for the final distinction.
Once the candidate set is small, add two or three forms to the comparison tray. The look-alike lab surfaces recognition text, count boundaries, checklists and source-review issues side by side.
Do not infer the electrical layer from the shell.
Documentation candidates, not an identification verdict, wiring map, mating test, signal converter recommendation or compatibility approval. Shape, keying, contact count and retention style do not establish protocol, wiring, voltage, current, direction, negotiated speed or device support.