RJ45 / Ethernet Connector Symbol
Definition: The RJ45 / Ethernet Connector symbol represents an 8P8C (8-position 8-contact) modular connector — standardised in IEC 60603-7 and TIA-568 — used to terminate Cat5e, Cat6, and Cat6A twisted-pair cables for Ethernet LAN connections, depicted in circuit diagrams with eight signal pins (Pin 1 TX+, Pin 2 TX−, Pin 3 RX+, Pin 6 RX−, and four unused pairs in 100BASE-T) and an optional Shield pin.
Also known as: RJ45, 8P8C connector, Ethernet connector, LAN connector, modular connector, network connector, patch cable connector, Cat5 connector.
What the RJ45 / Ethernet Connector symbol means
The RJ45 / Ethernet Connector symbol denotes the standardised physical interface between an Ethernet cable and network equipment. The 'RJ45' name (Registered Jack 45) is technically a misnomer — RJ45 is an 8P8C modular connector, the specific jack and plug system specified for UTP (Unshielded Twisted Pair) Ethernet cabling in TIA/EIA-568 and ISO/IEC 11801.
In circuit schematics and wiring diagrams the RJ45 connector symbol shows the eight pin positions (Pin 1 through Pin 8) following the T568A or T568B colour-coded wiring standard. In 100BASE-T (Fast Ethernet) and 10BASE-T (standard Ethernet), only four pins are active: Pin 1 (TX+), Pin 2 (TX−), Pin 3 (RX+), and Pin 6 (RX−). In 1000BASE-T (Gigabit Ethernet), all four pairs and all eight pins carry data simultaneously. A Shield pin is shown on screened (STP/ScTP) versions.
How to identify the RJ45 / Ethernet Connector symbol
The RJ45 / Ethernet Connector symbol is typically drawn as a rectangle representing the connector body with eight short parallel lines indicating the eight pin positions. Pins 1 through 8 are labelled from left to right as viewed from the cable-entry face of the plug. Shield appears as an additional terminal connected to the connector housing. In simplified block diagrams, the connector is shown as a labelled rectangle with a subset of active pins (P1 TX+, P2 TX−, P3 RX+, P6 RX−) and a Shield pin.
Function in a circuit
The RJ45 connector provides a mechanical and electrical interface for Ethernet twisted-pair cabling. The eight contacts correspond to the four twisted pairs in Cat5e/Cat6 cable; the differential signal pairs (TX+/TX−, RX+/RX−) carry Ethernet frames using 100BASE-TX or 1000BASE-T physical-layer encoding. The connector's 8P8C geometry allows error-free mating with standard Ethernet switches, routers, and network adapters. Magnetics (Bob Smith termination, common-mode choke) are typically integrated in the RJ45 socket on the PCB to provide impedance matching, isolation, and EMI suppression.
Standards: IEC vs ANSI
| IEC 60617 | IEC 60603-7 and ISO/IEC 11801 define 8P8C modular connectors for balanced twisted-pair cabling systems. ISO/IEC 11801 specifies Category 5e, 6, and 6A channel performance. The schematic symbol follows IEC 60617 connector conventions (rectangle with numbered terminals). |
|---|---|
| ANSI/IEEE 315 | TIA/EIA-568-B (now TIA-568-C) is the dominant North American standard for 8P8C Ethernet wiring, specifying T568A and T568B pin assignments. ANSI Y32.2 / IEEE 315 uses a numbered-terminal rectangle for connectors. IEEE 802.3 defines the Ethernet physical-layer standards that use the RJ45/8P8C connector. |
| Key difference | IEC (ISO/IEC 11801) and ANSI (TIA-568) both specify 8P8C connectors and identical pin usage for Ethernet. The T568A and T568B wiring colour codes differ (T568A: green pair on pins 1-2, orange pair on pins 3-6; T568B: orange pair on pins 1-2, green pair on pins 3-6) but produce electrically equivalent straight-through cables. Schematic symbols are identical between IEC and ANSI representations. |
Terminals / pins
| Pin | Name |
|---|---|
| p1 | Pin 1 (TX+) |
| p2 | Pin 2 (TX-) |
| p3 | Pin 3 (RX+) |
| p6 | Pin 6 (RX-) |
| shield | Shield |
Typical values
Connector type: 8P8C modular plug/jack (RJ45 informal name). Cable category: Cat5e (100 MHz), Cat6 (250 MHz), Cat6A (500 MHz). Ethernet standards supported: 10BASE-T, 100BASE-TX (pins 1,2,3,6), 1000BASE-T (all 8 pins), 2.5/5/10GBASE-T (all 8 pins, Cat6A+). Contact resistance: <20 mΩ (TIA-568). Mating cycles: ≥750 (TIA-568). Characteristic impedance: 100 Ω ±15% (balanced).
Where the RJ45 / Ethernet Connector symbol is used
- Wired LAN connections in homes, offices, and data centres connecting computers, switches, and routers
- IP camera and VoIP phone installations requiring PoE (Power over Ethernet, IEEE 802.3af/at/bt) delivery alongside data
- Industrial Ethernet networks (PROFINET, EtherCAT) using ruggedised M12 or standard RJ45 connectors
- PCB designs for network appliances, embedded Linux boards, and industrial controllers with onboard Ethernet
- Patch panels in structured cabling installations terminating horizontal runs from work area outlets
- Audio-visual systems using HDBaseT protocol for long-distance HDMI and control signal distribution over Cat5e/6 cable
Example
In an ESP32 Ethernet development board schematic, the RJ45 connector symbol shows Pin 1 (TX+) and Pin 2 (TX−) connected to the Ethernet PHY IC's transmit differential outputs, Pin 3 (RX+) and Pin 6 (RX−) connected to the PHY's receive differential inputs, and the Shield pin connected to chassis ground through a 1 nF / 2 kV capacitor (Bob Smith termination) to reduce EMI from cable shield currents.
Key facts
- The RJ45 / Ethernet Connector has eight signal contacts (Pin 1 through Pin 8) following TIA-568 / ISO/IEC 11801, plus a Shield terminal on screened versions; the key active pins for 100BASE-T are Pin 1 (TX+), Pin 2 (TX−), Pin 3 (RX+), and Pin 6 (RX−).
- The common name 'RJ45' is technically informal — the correct designation is 8P8C (8-position, 8-contact) modular connector per IEC 60603-7; however 'RJ45' is universally understood in the industry.
- T568A and T568B are the two standard wiring colour schemes for 8P8C connectors (TIA-568); both are electrically equivalent for straight-through cables — mixing T568A and T568B between both ends creates a crossover cable.
- 1000BASE-T (Gigabit Ethernet, IEEE 802.3ab) uses all four twisted pairs (all eight pins) simultaneously in full-duplex bidirectional operation with five-level PAM-5 encoding, requiring Cat5e or better cable.
- PoE (Power over Ethernet, IEEE 802.3af/at/bt) delivers DC power over the same RJ45 cable as data — 802.3af provides 15.4 W, 802.3at 30 W, and 802.3bt up to 90 W per port.
- The integrated magnetics (transformer + common-mode choke) typically found in the PCB-mount RJ45 jack (RJ45 with magnetics) provide 1500 V AC galvanic isolation between the cable and the PHY circuit, EMI suppression, and 100 Ω impedance transformation.
- Maximum specified cable segment length for 10/100/1000BASE-T is 100 metres (328 ft) from switch to device per TIA-568 and ISO/IEC 11801, including patch cable lengths at both ends.
Diagrams that use this symbol
- switch diagram in networking
- phone line wiring diagram
- phone wiring diagram
- 4 wire phone jack wiring diagram
- poe wiring diagram
- cat5 diagram
- earphone wiring diagram
- telephone jack wiring diagram
Frequently asked questions
What does the RJ45 connector symbol mean in a circuit diagram?
The RJ45 / Ethernet Connector symbol represents an 8P8C modular connector used to terminate Ethernet cables. It shows the eight pin positions (Pin 1 TX+, Pin 2 TX−, Pin 3 RX+, Pin 6 RX− for 100BASE-T; all eight pins for Gigabit) and an optional Shield terminal, indicating the physical interface between a PCB and a network cable.
What does the RJ45 connector symbol look like on a schematic?
The RJ45 symbol is drawn as a rectangle representing the connector body with eight numbered terminal lines (P1–P8) plus a Shield terminal. Active Ethernet pins are labelled with their function (TX+, TX−, RX+, RX−). In simplified block diagrams, only the active pins for the specific Ethernet speed are shown.
What is the difference between T568A and T568B wiring?
T568A and T568B are two colour-code wiring sequences for 8P8C connectors per TIA-568. T568A places the green pair on pins 1-2 and orange on pins 3-6; T568B places orange on pins 1-2 and green on pins 3-6. Both produce identical electrical performance for straight-through Ethernet cables; mixing both ends creates a crossover cable. T568B is more common in North America; T568A is specified for US government installations.
What standard defines the RJ45 Ethernet connector?
IEC 60603-7 and ISO/IEC 11801 define the 8P8C modular connector and its cabling system performance categories. TIA/EIA-568-C (now TIA-568-D) is the North American wiring standard specifying T568A/B pin assignments. IEEE 802.3 defines the Ethernet physical-layer standards (10/100/1000BASE-T) that use the RJ45/8P8C connector.
How many pins does an RJ45 connector have?
An RJ45 (8P8C) connector has eight contacts (pins). For 10BASE-T and 100BASE-TX Ethernet, only four pins are active: Pin 1 (TX+), Pin 2 (TX−), Pin 3 (RX+), and Pin 6 (RX−). For 1000BASE-T (Gigabit Ethernet), all eight pins carry data as four bidirectional differential pairs.
What is the maximum cable length for an RJ45 Ethernet connection?
The maximum specified segment length for 10BASE-T, 100BASE-TX, and 1000BASE-T Ethernet over Cat5e/Cat6 cable is 100 metres (328 ft) from switch port to end device, per TIA-568 and ISO/IEC 11801. This includes all patch cables at both ends. Exceeding 100 m may cause excessive attenuation and link errors.
Can an RJ45 connector deliver power as well as data?
Yes. Power over Ethernet (PoE) — defined in IEEE 802.3af (15.4 W), IEEE 802.3at (30 W), and IEEE 802.3bt (up to 90 W) — delivers DC power to devices such as IP cameras, VoIP phones, and access points over the same Cat5e/6 cable and RJ45 connector as the Ethernet data signal, eliminating the need for a separate power supply at the device.
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