[Galaxy S 4 Active General] O-T:
If you wonder what is baseband, baseband version, GSM modem, LTE/4G modem, and find time to read and courtesy to suppress the urge to ask same question recently explained -

... here is a treat for you:

MODEM.BIN and NON-HLOS.BIN HOW-TO flash using Odin

Alternative solution

Thanks @Formhault

What version of modem.bin can you flash?

Thanks @hawkerpaul

Make sure you have non-hlos.bin and bootloader version match:

http://xdaforums.com/showthread.php?p=62994941

Samsung lettercode

decoded for firmware/bootloader/modem

Example: I9295XXUCNE4

I9295 = phone model

XXU = baseband (XXU is Global, valid almost everywhere, any country regardless of carrier)

C = baseband build version

NE4 = datecode

Datecode

N = year = 2014 (14th letter of alphabet)

E = month of year (May in this case, 5th letter of the alphabet)

A = build # of that month (10th for, "A", as they start 1-9, then letters)

NE4 = 2014, May, Build 4

NE5 = 2014, May, Build 5

NH2 = 2014, Aug, Build 2

Identify your bootloader

Make sure you have LTE/ audio/ network certificate (=NON-HLOS.bin) version matching your bootloader (=ABOOT, SBL*, TZ) version. Reason explained in 1st post.

NON-HLOS.bin inside the apnhlos partition /firmware and the bootloader is never updated or downgraded by AOSP/CM ROMs or custom recovery flashing. Some customized stock ROMs may mess with the relationship between bootloader and NON-HLOS.bin. Or you have messed up because you wanted to have the latest modem and flashed a *N-- version NON-HLOS.bin on your *M-- version bootloader. This will have bad impact on sound and WiFi functionality leading to you can not activate WiFi.

Earlier versions of PhilZ CWM recovery had an option to wipe partitions

/firmware

(LTE, audio, network certificate, NON-HLOS.bin)

/firmware-mdm

(GSM-modem, MODEM.BIN)

This wipe was not needed because flashing to this partitions overwrite the existing content. Wiping the same partitions without flashing modem or complete stock ROM can render telephone, audio and network functionality useless.

The partitions /firmware and /firmware-mdm is removed from later PhilZ Recovery fstab.

Ref. PhilZ Recovery 6.23.9 change log http://xdaforums.com/showpost.php?p=51389599&postcount=3520

Identify bootloader and select corresponding NON-HLOS.bin

NON-HLOS.bin is also called

LTE-modem

or

WiFi-fix

when discussed in xda-forum

1. Connect phone from ADB or use Terminal app and do this command:

getprop ro.bootloader

( ADB =Android Debug Bridge )

The output is

Samsung lettercode

and will tell what version of bootloader you currently have.

2. Select version of NON-HLOS.bin to flash according to

3rd last letter

of

Samsung lettercode

bootloader:

BOOTLOADER 3rd last letter = NON-HLOS.bin 3rd last letter

I9295xxxxMxx = I9295xxxxMxx JellyBean 4.2.x

I9295xxxxNxx = I9295xxxxNxx KitKat 4.4.x

I9295xxxxOxx = I9295xxxxOxx Lollipop 5.0.x
​

Not known exactly what's first version of i9295 firmware/bootloader that has Knox feature. Strong indications nominate all KitKat 4.4.x to have it on QualComm based phones. And GT-I9295 has QualComm chipset.

Updating bootloader to a higher version should not trigger Knox 0x1, but downgrade Knox featured bootloader may cause that.

Status of KNOX is shown in Download Mode upper left corner of screen.

This S4 thread discuss the limitation introduced by Knox:

http://xdaforums.com/showthread.php?p=45666586