DEV Community: Voohu Electronic Tech

RJ45 Jack Layout for Video Conferencing Room Controllers: Cable Access, Port Labels, and Installation Checks

Voohu Electronic Tech — Thu, 30 Jul 2026 23:39:48 +0000

Video conferencing room controllers are usually installed where appearance matters: behind a display, inside a credenza, under a table, or in a shallow wall enclosure. Those locations make a PCB-mounted RJ45 female jack a mechanical design problem as much as an Ethernet interface. A port that looks fine on an open bench can be difficult to connect once the controller is surrounded by brackets, power leads, and audiovisual cabling.

The first layout choice is port orientation. A right-angle RJ45 jack sends the plug and cable sideways relative to the PCB, which can be useful in a low-profile controller. A vertical jack sends the cable away from the board, which may suit a deeper enclosure. Neither orientation is automatically better. The correct choice depends on the actual distance to the back cover, the cable approach direction, and the hand clearance needed to release the plug latch.

Labels deserve the same attention. Room installations often include more than one Ethernet lead: a network uplink, a control link, or a temporary service cable. A clear label placed next to the RJ45 opening is much easier to use than one hidden under the cable. If the product uses port LEDs, make sure that the light path remains visible after the controller is fitted into its intended location. A status light that is covered by a cabinet edge provides little help during commissioning.

Internal cable routing is another common source of late changes. Do not route power wiring or stiff harnesses across the plug release area. Do not rely on an installer to make an unusually tight cable bend simply because the CAD view leaves a few millimetres of space. Model a realistic plug body and a representative cable exit in the enclosure assembly, then verify that the cover can close without loading the connector.

A shielded RJ45 jack should be selected and grounded according to the product’s approved electrical and mechanical design. The metal shell alone does not define the final result. Board contacts, enclosure material, mounting hardware, and cable type all affect the finished appliance. The useful design question is therefore not merely “is the jack shielded?” but “how is the selected jack integrated into this controller’s complete grounding and enclosure arrangement?”

Use a short installation review before the design is released:

Confirm the selected RJ45 jack footprint against the latest component drawing.
Check plug insertion, latch release, and cable exit with the production enclosure.
Verify that labels and status indication remain visible in the mounted position.
Reserve clearance around shield features and board-side support points.
Ask an installer to perform a connection and replacement trial using the intended mounting location.

When these checks happen early, the Ethernet port becomes a quiet part of the room-controller experience: easy to find, easy to connect, and easy to service after the furniture and display are already in place.

Fitting an RJ45 Jack Into a Narrow DIN-Rail Ethernet-to-Serial Gateway: 7 Mechanical Checks

Voohu Electronic Tech — Thu, 30 Jul 2026 00:44:39 +0000

DIN-rail Ethernet-to-serial gateways often have very little room behind the front face. The RJ45 female socket has to fit alongside terminal blocks, status labels, mounting features, and the cable route inside a compact housing. A successful port layout comes from checking the complete enclosure early, not from choosing the smallest connector that appears to fit in a board view.

1. Confirm the real cable approach

Look at how the gateway will be installed on the rail. A cable may need to enter from the front, top, bottom, or side depending on the cabinet layout. The RJ45 jack orientation should support that route without blocking neighboring hardware or creating an impractical bend at the plug.

2. Reserve latch clearance

The plug latch must remain reachable after the gateway is installed. A deeply recessed port or a label placed too close to the opening can make an ordinary unplugging task unnecessarily difficult. Test the layout with the expected connector boot, not only with a bare plug.

3. Check the housing depth

Narrow DIN-rail enclosures can limit the distance available behind the port face. Compare the connector’s front-to-back body depth, retention features, and PCB keep-out area with the internal wall, rail clip, and adjacent components. Use the current drawing for this comparison.

4. Match the PCB footprint exactly

Two single-port RJ45 jacks can have different solder-tail patterns, mounting posts, shell tabs, and LED pin locations. The approved PCB footprint must match the selected model. Do not reuse a footprint merely because another socket has a similar outline.

5. Keep labels readable

Commissioning teams often work with several similar gateways in the same cabinet. Make the Ethernet port label visible after the cable is connected. If the product has a maintenance port or multiple network connections, define the label sequence clearly before enclosure artwork is finalized.

6. Review service loading

Cable movement transfers mechanical load to the port. Review the RJ45 socket’s retention features, the PCB support around the footprint, and the surrounding housing. A layout that works on an open bench may be less forgiving when a technician reaches into a crowded control cabinet.

7. Align any shield decision with the full installation

If a shielded RJ45 jack is specified, review the cable type, enclosure strategy, grounding approach, and validation plan together. The shell is one element of a complete interface decision, not an isolated fix for every installation condition.

Release checklist

Before finalizing a DIN-rail gateway port, document the enclosure drawing, rail orientation, cable approach, connector drawing, panel opening, label plan, expected service cycle, and assembly method. A correctly selected RJ45 female socket helps the gateway remain accessible and serviceable even when cabinet space is limited.

PoE Wireless Access Points Need More Than an Ethernet Socket: Practical RJ45 Jack Selection Checks

Voohu Electronic Tech — Tue, 28 Jul 2026 23:39:13 +0000

An Ethernet port on a wireless access point can carry both network data and power, but the RJ45 jack still has to satisfy mechanical, thermal, and service requirements in the finished access point. Choosing an RJ45 female socket only by appearance can create avoidable issues after the board is mounted inside a ceiling, wall, or enclosed housing.

Begin with the installed access point

Access points are often installed where technicians have limited room to plug in a cable: above a ceiling tile, against a wall, or under a protective cover. The RJ45 port should be easy to reach with the expected cable and plug boot. Confirm cable entry direction, bend radius, latch access, and clearance around the port before finalizing the connector orientation.

Right-angle and vertical RJ45 jacks can both be appropriate. The better choice depends on the PCB position and the intended cable path in the enclosure. Review the actual mechanical drawing rather than assuming that one package style will fit every access-point layout.

Separate connector selection from system-level power design

Power-over-Ethernet applications require the port, cable, PCB, housing, and system validation plan to be considered together. The RJ45 jack is an important part of the interface, but it is not a substitute for validating the complete power and thermal design.

Use the current connector drawing and qualification data to verify the selected part for the intended Ethernet and power application. Then review the surrounding board area for copper layout, component clearance, ventilation, cable strain relief, and expected operating conditions. Avoid making conclusions from a generic image or an unrelated part number.

Keep shielding and enclosure strategy aligned

If the design uses a shielded RJ45 female socket, decide how the connector shell relates to the cable shield, the housing, and the grounding strategy. A metal shell can be useful in a system-level EMC approach, but the result depends on the complete installation. The cable type, enclosure construction, and validation method matter as much as the connector selection.

Make commissioning easy

LED visibility can be especially valuable when an access point is installed overhead or behind a cover. Check that link and activity indicators remain visible after the cable is connected and the product is closed. Place labels where a technician can identify the port without removing the unit.

A concise specification checklist

Before releasing an RJ45 jack for a PoE wireless access point, collect:

Mounting orientation and cable exit direction
Enclosure drawing and port opening details
Ethernet rate and intended power application
Shield requirement and grounding concept
LED color, function, and visibility requirement
Assembly process and approved PCB footprint
Expected ambient conditions and service cycle

The best RJ45 jack is the one that works cleanly in the complete installed access point—not just the one that fits an unreviewed PCB footprint.

SMT or DIP RJ45 Jack? Practical Assembly Trade-Offs for Ethernet PCB Designers

Voohu Electronic Tech — Tue, 28 Jul 2026 01:05:47 +0000

An RJ45 jack is both an electrical interface and a mechanical interface. That is why choosing SMT or DIP construction should start with the actual assembly process and expected cable use, not just with a preference for one PCB technology.

For Ethernet hardware teams, the question is usually not “Which option is newer?” It is “Which RJ45 female socket gives this product the right balance of assembly efficiency, mechanical retention, board layout freedom, and service life?”

SMT RJ45 jacks: efficient placement, careful mechanical planning

Surface-mount RJ45 jacks can support automated placement and may fit layouts where component placement density matters. Depending on the model, they can help keep routing and assembly on a single PCB side or integrate effectively with a controlled production process.

However, SMT does not remove the need for mechanical design. The port still receives cable insertion forces, so the selected model’s shield tabs, mounting lugs, board support, and enclosure interface need to be reviewed together.

Use an SMT option when these questions have clear answers:

Does the pick-and-place and reflow process support the exact connector package?
Is the recommended solder land pattern implemented exactly from the drawing?
How is mating force transferred away from small signal pads?
Is the PCB adequately supported near the port opening?
Can the panel or housing help absorb cable-side load?

DIP RJ45 jacks: robust hole-based retention, different routing constraints

DIP, or through-hole, RJ45 jacks use plated holes for their signal pins and often for mechanical features. This can provide a familiar, robust construction for Ethernet ports that are likely to be plugged and unplugged during installation or service.

The trade-off is that through-hole patterns occupy routing space and must align with drill, plating, soldering, and panel constraints. A DIP part may be an excellent choice for a durable industrial controller, but it should be selected with an early view of layer count, board edge, and wave or selective-solder capability.

Compare production flow, not only the connector body

The correct choice depends on the whole manufacturing sequence. Review the exact model with production engineering before approving the part.

Decision area	SMT RJ45 jack	DIP RJ45 jack
Assembly approach	Reflow-capable placement process	Through-hole solder process, often wave or selective solder
PCB routing	May preserve holes but requires pad keep-outs	Uses plated holes and can constrain local routing
Mechanical review	Retention tabs and enclosure support are especially important	Hole-based features can add retention, but panel support is still needed
Footprint control	Precise land pattern and coplanarity are important	Hole size, tolerance, and solder fill need confirmation

This is a planning comparison, not a universal performance ranking. The exact connector family and product enclosure can change the best answer.

Do not copy a footprint from a similar part

RJ45 connectors may look alike yet have different pin spacing, shield-tab geometry, LED configuration, port height, and mechanical posts. An SMT version and a DIP version of a family can also differ in the panel relationship.

Before release, verify the current part drawing for:

Signal pin coordinates
Shield/ground connections
Mechanical posts or solder tabs
Recommended pad or hole dimensions
Component height and keep-out area
Reflow, wave, or selective-solder recommendations

Build the mechanical path into the design review

An RJ45 female socket should not be treated as a small signal component at the end of the board. Review the force path from the cable plug through the jack, PCB, standoffs, panel, and enclosure. This is especially important for equipment that is frequently serviced, mounted in a cabinet, or exposed to vibration.

What to send for a useful connector recommendation

Provide the supplier with the intended PCB technology, assembly process, port orientation, required data rate, shielding decision, product enclosure drawing, and expected service conditions. VOOHU’s RJ45 range includes SMT and DIP options, but final qualification should use the exact part drawing and a production-representative board.

The best outcome is not simply a smaller or cheaper connector. It is an Ethernet port that can be assembled consistently and survives the way the finished equipment will be installed and maintained.

Choosing 1xN, 2xN and Stacked Multi-Port RJ45 Jacks for Ethernet Switches

Voohu Electronic Tech — Mon, 27 Jul 2026 06:49:49 +0000

If you are laying out an Ethernet switch, treating every RJ45 port as an isolated single-port component is a fast way to lose board space, front-panel clarity, and serviceability.

Multi-port RJ45 jacks are worth considering when the device needs a repeated row or stack of female Ethernet sockets. VOOHU's RJ45 material includes 1xN and 2xN multi-port configurations, alongside discrete and integrated RJ45 interfaces.

Here is the selection checklist I would use before locking the mechanical layout.

1. Start with the visible port map

Ask what the user sees on the front panel:

How many Ethernet ports are exposed?
Do ports need to be arranged in one row, two rows, or a mixed layout?
Is there a clear port-numbering convention?
Is there room for plugs with larger cable boots?
Are there nearby buttons, vents, USB openings, or indicator windows competing for space?

A 2xN stack can save panel width, but it also changes vertical clearance, label placement, and how easily a technician can remove a cable from the lower row.

2. Pick the package around assembly constraints

The package should match the PCB and enclosure, not just the port count.

Need a shallow front-to-back layout?   -> check low-profile and board-clearance limits
Need dense front-panel ports?          -> compare 1xN with 2xN stack geometry
Need an automated board process?       -> verify the approved mount style
Need a serviceable front panel?        -> check plug, latch, and cable-boot access
Need port status visibility?           -> reserve a clear indicator and label area

VOOHU offers discrete and multi-port RJ45 formats, including 1xN and 2xN configurations. Confirm the exact part drawing before copying a footprint between layouts: port pitch, retention features, mounting pins, and panel alignment are model-specific.

3. Design for serviceability, not only density

In a switch, a port that looks dense in CAD can be frustrating in a rack or cabinet. Check these points with a real cable or a dimensional plug model:

Can the latch be reached without disturbing the adjacent cable?
Are upper and lower ports equally accessible in a stacked arrangement?
Are the port IDs still visible after all ports are connected?
Is the cable exit direction compatible with the enclosure and rack position?
Does the layout leave a sensible path for replacement or inspection?

4. Keep LED and labeling decisions tied to the port plan

Link, activity, and speed indication are most useful when the operator can associate them with the correct port instantly. Do not add indicator windows after the connector pitch has already been fixed. Plan port numbers, LED visibility, and cable-routing space together.

5. Use a short RFQ checklist

For a multi-port RJ45 jack request, include:

Port count and desired arrangement: 1xN or 2xN
Target device: switch, router, hub, or other network equipment
Mount style and board thickness
Front-panel clearance and maximum height/depth
Port labels and indicator requirement
Shielding requirement, if applicable
Required data-rate and project validation requirement

The best multi-port RJ45 choice is the one that keeps the port map readable, the cables serviceable, and the PCB/enclosure interfaces aligned from the first prototype.

RJ45 Jack or SFP Cage? A Copper-vs-Fiber Decision Guide (VOOHU)

Voohu Electronic Tech — Fri, 24 Jul 2026 06:43:06 +0000

TL;DR: A fixed RJ45 copper jack (8P8C 母座) and an SFP fiber cage solve different problems. RJ45 wins on cost, power (PoE) and density; SFP wins on reach, rate and field flexibility. VOOHU makes both, and the most common right answer is: put both on the board.

At a glance

RJ45 jack (copper 8P8C socket): twisted-pair Cat5e/6/6A, 10/100M–10GBASE-T, up to 100 m (TIA-568/ISO 11801), carries PoE (802.3af/at/bt), ~1.5 kV magnetics isolation. Medium is fixed at design time.
SFP cage (pluggable MSA): hosts an optical module or DAC; 5G–400G (up to QSFP112); ~100 m DAC, ~300–400 m MMF, 10–80 km SMF (per IEEE 802.3 optics); no power over fiber; galvanic isolation inherent; swap the module to change reach/medium with no board respin.

Where each wins

RJ45: cost per port, powering the far end (cameras, APs), and port density.
SFP: long reach, higher rates, and future-proofing (change optics, not the board).

The decision path

Does the far end need power over the cable? -> RJ45 (PoE).
How far is the link? >100 m -> fiber/SFP.
What rate? >10G -> SFP.
Need medium flexibility or isolation over distance? -> SFP.

The pattern most designs land on

Put an RJ45 jack and an SFP cage on the same board: copper for powered/short links, an SFP uplink for reach and rate. VOOHU supplies both sides.

Full guide + comparison table + FAQ: https://voohuelectronic-ux.github.io/voohu-rj45-guide/resources/rj45-jack-vs-sfp-copper-vs-fiber.html

VOOHU Electronics | https://www.voohuele.com | olivia@voohuele.com

The RJ45 Jack Behind HDBaseT Is Doing 16 Gbit/s and 100 W — Here's What to Spec (VOOHU)

Voohu Electronic Tech — Fri, 24 Jul 2026 02:10:52 +0000

TL;DR: HDBaseT runs uncompressed UHD video + audio + Ethernet + control + up to 100 W over one Cat cable, terminated in a normal-looking 8P8C RJ45 jack (母座). But it demands a shielded, Cat6A-grade socket — not a generic data jack. Figures below are from the HDBaseT Alliance, IEC 60603-7, ANSI/TIA-568 and IEEE 802.3.

What HDBaseT asks of the jack

Up to 16 Gbit/s downstream -> shielded jack to Cat6A performance; tight return loss & NEXT
Up to 100 m on Cat5e/Cat6 -> low insertion loss, controlled 100 Ω differential impedance (IEC 60603-7)
PoH up to 100 W over 4 pairs (based on 802.3at) -> high per-port current (VOOHU 350 mA–1.5 A); magnetics that don't saturate under DC bias
Isolation -> ≥1500 Vrms (magjack option)
Noisy AV racks -> metal shielded housing, EMI tabs/gasket, chassis-ground return
Life -> -40~+85 °C, ≥750 mating cycles (IEC 60603-7)

Magjack vs plain shielded

A shielded integrated-magnetics jack puts Cat6A-grade magnetics right at the connector — cleanest for AV. Plain shielded + board magnetics works if layout is disciplined.

VOOHU magjack (representative datasheet)

1CT:1CT ±2% turns ratio · 350 µH OCL min · insertion loss ≤1.0 dB (1–100 MHz) · return loss ≥18 dB (1–30 M) -> ≥10 dB (80–100 M) · crosstalk ≥40 dB (1–30 M) · CMR ≥30 dB · Hi-Pot 2250 VDC (exceeds IEEE 802.3 1500 Vrms).

Full guide: https://voohuelectronic-ux.github.io/voohu-rj45-guide/resources/rj45-jacks-for-hdbaset.html

VOOHU Electronics | https://www.voohuele.com | olivia@voohuele.com

RJ45 Jack or SFP Cage? A Copper-vs-Fiber Decision Guide (VOOHU)

Voohu Electronic Tech — Fri, 24 Jul 2026 02:07:50 +0000

At a glance

RJ45 jack (copper 8P8C socket): twisted-pair Cat5e/6/6A, 10/100M–10GBASE-T, up to 100 m (TIA-568/ISO 11801), carries PoE (802.3af/at/bt), ~1.5 kV magnetics isolation. Medium is fixed at design time.
SFP cage (pluggable MSA): hosts an optical module or DAC; 5G–400G (up to QSFP112); ~100 m DAC, ~300–400 m MMF, 10–80 km SMF (per IEEE 802.3 optics); no power over fiber; galvanic isolation inherent; swap the module to change reach/medium with no board respin.

Where each wins

RJ45: cost per port, powering the far end (cameras, APs), and port density.
SFP: long reach, higher rates, and future-proofing (change optics, not the board).

The decision path

Does the far end need power over the cable? -> RJ45 (PoE).
How far is the link? >100 m -> fiber/SFP.
What rate? >10G -> SFP.
Need medium flexibility or isolation over distance? -> SFP.

The pattern most designs land on

Put an RJ45 jack and an SFP cage on the same board: copper for powered/short links, an SFP uplink for reach and rate. VOOHU supplies both sides.

Full guide + comparison table + FAQ: https://voohuelectronic-ux.github.io/voohu-rj45-guide/resources/rj45-jack-vs-sfp-copper-vs-fiber.html

VOOHU Electronics | https://www.voohuele.com | olivia@voohuele.com

RJ45 Jacks for HDBaseT: the socket spec AV-over-Cat actually needs

Voohu Electronic Tech — Fri, 24 Jul 2026 01:52:40 +0000

TL;DR — HDBaseT reuses the standard 8P8C RJ45 jack, but the socket carries up to 16 Gbit/s of video and up to 100 W of PoH. Spec it as shielded, Category 6A-grade, and high-current — not as a commodity data port.

The RJ45 jack (母座) is the part people forget in an HDBaseT design. Here's what the standard actually asks of it.

What HDBaseT puts through the connector (HDBaseT Alliance)

Up to 16 Gbit/s downstream, 2 Gbit/s up
Up to 100 m on Cat5e/Cat6
100 Mb Ethernet + control + audio
PoH up to 100 W across four pairs, based on IEEE 802.3at

What that means for the jack you order

Shielded (FTP/STP), metal housing, shield tabs grounded to chassis — UTP invites EMC failures
Category 6A performance, controlled 100 Ω interface (IEC 60603-7) — Cat5e-grade has no margin for 4K/8K
High per-port current (350 mA–1.5 A) so the jack/magnetics don't saturate under PoH DC
Magnetics choice: integrated (magjack) for a compact port, or discrete for independent tuning
−40…+85 °C grade + ≥750 mating cycles for rack/outdoor life

VOOHU's integrated RJ45 line lists HDBaseT among supported modes (10/100M, 1G, 2.5G, 5G, 10GBASE-T, HDBaseT) with the current grades, shielding and temp range above. Their Gigabit magjack datasheet (SYT511) shows the electrical bar: 1CT:1CT ±2%, 350 µH OCL, ≤1.0 dB IL, ≥30 dB CMR, 2250 VDC isolation.

Full write-up + spec table: https://voohuelectronic-ux.github.io/voohu-rj45-guide/resources/rj45-jacks-for-hdbaset.html

VOOHU Electronics · voohuele.com · olivia@voohuele.com

Locking RJ45: Why Stage and Factory Ports Don't Use a Bare RJ45 Jack (VOOHU)

Voohu Electronic Tech — Thu, 23 Jul 2026 07:48:34 +0000

TL;DR: The RJ45 retention mechanism is a moulded plastic tab. It snags, snaps, and vibrates loose. An XLR RJ45 latching connector is a standard 8P8C jack (母座) in a rugged XLR-format metal shell with a positive lock — same IEC 60603-7 contacts, far better mechanics.

Three ways a bare RJ45 fails in the field

The latch snaps. Tab catches on a cable bundle, shears off; plug is now held by friction.
Vibration walks the plug out. Presents as intermittent packet loss, not a clean disconnect — much harder to diagnose.
Cable weight levers the contact. A heavy vertical drop applies constant moment, degrading contact force.

What XLR RJ45 gives you

Locking: latch lock / internal card / spiral (threaded) lock
IP67 ingress protection
1000 mating cycles vs the 750-cycle IEC 60603-7 minimum
1.5 A per contact (DC), covering PoE / PoE+ / PoE++
-40~+85C, 20-70% humidity
180 straight-through, 180 plug board, 90 adapter / plug board

Gotchas

The lock + seal are in the shell. A plain RJ45 patch cord mates electrically and gives zero retention. Spec the matching XLR plug.
These are big bodies (up to ~41.5 mm on one axis). Check the panel cut-out and depth before tooling the enclosure.
Continuous vibration? Use the spiral (threaded) lock, not the quick latch.
Static indoor rack? Don't bother — a good standard jack is the better economic choice.

Full guide + spec matrix: https://voohuelectronic-ux.github.io/voohu-rj45-guide/resources/xlr-rj45-latching-connectors.html

VOOHU Electronics | https://www.voohuele.com | olivia@voohuele.com

RJ45 Jack Mounting Angle Cheat-Sheet: Right-Angle vs Vertical vs 45 (VOOHU)

Voohu Electronic Tech — Wed, 22 Jul 2026 01:55:23 +0000

TL;DR — For an RJ45 jack (the female 8P8C socket / 母座), the mounting angle drives your PCB floor plan and enclosure height. Right-angle for front panels, vertical to save board width, 45° for slim faceplates. It's a mechanical choice, not a bandwidth one.

The three angles

Right-angle (90°, horizontal / side-entry): plug enters parallel to the board, port faces the panel edge. Default for switches / routers / 1U rack. Shortest route to the PHY.
Vertical (180°, upright / top-entry): plug enters from above. Narrow footprint reclaims horizontal board width on stacked modules and daughter-cards.
45° (inclined): angled exit for patch panels, AV wall plates and slim faceplates — protects the cable bend radius.

Gotcha

The 90° / 180° labels are not consistent between vendors. One brand's "180°" is another's side-entry. Read the mechanical drawing, not the number.

Specs that don't change with angle (IEC 60603-7 / ANSI-TIA-568 8P8C)

Data rate: 10/100M → 10GBASE-T
PoE: up to 1.5 A per contact
Durability: 750 mating cycles (min)
Contact resistance: ≤20 mΩ
Mount: DIP or SMT · Tab: up / down
Temp: 0~+70°C up to −40~+105°C industrial
Optional integrated magnetics (MagJack): OCL 350 µH, 1CT:1CT, 2250 VDC isolation, insertion loss ≤1.0 dB

VOOHU catalogs all three angles (45° / 90° / 180°) in one RJ45 jack family. Full write-up:
https://voohuelectronic-ux.github.io/voohu-rj45-guide/resources/rj45-jack-mounting-angle-right-angle-vs-vertical.html

RJ45 Jack vs SFP Port: Copper or Fiber? (A Hardware Selection TL;DR)

Voohu Electronic Tech — Wed, 22 Jul 2026 00:52:22 +0000

TL;DR — An RJ45 jack is a fixed copper 8P8C socket; an SFP port is an empty cage for a pluggable optic or DAC. Copper jack for short/cheap/PoE links, SFP for long/fast/fiber uplinks. Most boards use both.

RJ45 jack (the copper socket / 母座)

Medium fixed at design time: twisted-pair copper, up to 100 m (TIA-568).
VOOHU range: 10/100M, 1G, 2.5G, 5G, 10GBASE-T.
Carries PoE (802.3af/at/bt) — contact current to 1.5 A. Only the copper jack can power the far end.
Cheap, dense, DIP or SMT, magjack or discrete, shielded options.

SFP port (the pluggable cage)

Not a transceiver — an SFF-MSA cage + connector for a hot-pluggable module.
VOOHU range: SFP/SFP+/SFP28/QSFP...QSFP112, 5G to 400G.
Fiber reach: ~300 m MMF to 10-80 km SMF; or short copper via DAC.
No power over the link. Optics run hot — vent/heat-sink the cage.

Decide fast

Needs PoE? -> RJ45 jack.
Over 100 m or cross-building? -> SFP fiber.
Up to 10G and up to 100 m? -> RJ45 jack (cheaper).
25G+ or medium flexibility? -> SFP.

Gotcha: no PoE over fiber; don't buy an SFP + optic for a short 10G copper hop.

Full write-up with spec tables (VOOHU makes both the jack and the cage): https://voohuelectronic-ux.github.io/voohu-rj45-guide/resources/rj45-jack-vs-sfp-copper-vs-fiber.html