The KSZ9031RNXCA is a Gigabit Ethernet transceiver from Microchip. It is made to support data transmission over typical CAT-5 shielded twisted pair cable. 

Here is a simple interpretation of an application circuit using the KSZ9031RNXCA: 

1. Power Supply: The KSZ9031RNXCA operates with a core supply voltage of 1.2V and an I/O supply voltage of 3.3V. The device supply pins (VDD_CORE, EDDA_1V2, EDDA_3V3, and VDDD_3V3) should have decoupling capacitors placed closely for power supply stability. 

2. Ethernet Input/Output: The KSZ9031RNXCA contains a Physical Coding Sublayer (PCS) and Physical Medium Dependent (PMD) for data transfer. The PMD connects to the RJ-45 Ethernet port via the RXP/RXN and TXP/TXN pins. Magnetic would be placed in-between for signal isolation. 

3. MAC Interface: This device provides a Reduced Gigabit Media Independent Interface (REMIX) for data and control interface between the Ethernet MAC in your system and the KSZ9031RNXCA. The REMIX interface uses the TXD, TLC, RED, ROC, GTXC pins and the control pins (MDC, MDI). 

4. Clock Input: If using the REMIX interface, an external 25 MHz clock source should be provided at the REFLEX pin to synchronize data transfers.

5. Reset and Interrupt: To reset the device, use the RESET pin. INTO is an interrupt pin used to signal status change events to the system processor. 

6. LED Outputs: LED[0] to LED[2] are output pins that can be configured to indicate different Ethernet link and activity statuses. They're typically connected to LEDs. 

Remember, this is a general guide and the exact application circuit would depend on the specific use case. Always refer to the KSZ9031RNXCA data sheet and other technical resources from Microchip for more details when designing the application circuit.