How "show inventory" displays SX SFP?

Question

I've a Cisco 3925 and it's not quite clear why an "1000BASE-SX SFP" entry is visible in the inventory. Is it only visible when the SX SFP is in use? (I've no chance to modify it.)

NAME: "CISCO3925-CHASSIS", DESCR: "CISCO3925-CHASSIS"
PID: CISCO3925-CHASSIS , VID: V02

NAME: "Cisco Services Performance Engine 100 for Cisco 3900 ISR on Slot 0", DESCR: "Cisco Services Performance Engine 100 for Cisco 3900 ISR"
PID: C3900-SPE100/K9   , VID: V01

**NAME: "1000BASE-SX SFP", DESCR: "1000BASE-SX SFP"
PID: GLC-SX-MMD        , VID: 001**

NAME: "C3900 AC Power Supply 1", DESCR: "C3900 AC Power Supply 1"
PID: PWR-3900-AC       , VID: V02

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Gi0/0   << RJ45
Gi0/1   << Combo port using RJ45
Gi0/2   << Combo port using SX

Answer 1

If you have an SFP module inserted, you will see the specific type.

You can choose to specifically use the inserted SFP, or choose to use the built-in copper connector, with the media-type interface command:

interface GigabitEthernet0/1
 media-type sfp

or

interface GigabitEthernet0/1
 media-type rj45