Return true or false depend if the given feature is available. Here are some examples of valid arguments (without quotes) :

• ALS_SENSOR - the phone has an Ambient Light Sensor
• BW_BDF_DISP - the phone's display uses fonts in Glyph Bitmap Distribution Format to display texts
• ETH_SWITCH_DEVICE -  the phone has Ethernet switch capability (true for all current phone types)
• FEATURE_EAP_TLS - the phone has support for EAP (https://en.wikipedia.org/wiki/Extensible_Authentication_Protocol)
• FEATURE_HEADSET_DETECT - the headset detection feature stops users from switching to headset if no headset is connected (for example on D735, D335, D717)
• FEATURE_LABEL_DISPLAY - the phone has a label display
• FEATURE_PUI_STYLE_SIO - phone uses the 'new' color UI (true for all phones with color display on version 10.x)
• FEATURE_SECOND_DISPLAY - the phone has a second display
• FEATURE_SMART_LABEL - the phone has smart labels (ex: D735, D717)
• FEATURE_STANDARD_SMART_LABEL - a subtype of smart label called standard smart label is available (ex: D717)
• FEATURE_USB_SUPPORT - the phone has USB support
• FEATURE_XMPP - the phone has support for XMPP (https://xmpp.org/)
• HAS_GBIT_PHY - the phone has a gigabit Ethernet port
• HAS_LARGER_PIXEL_SIZE - has the color display with larger pixels than the rest of the phones (true for D765)
• IPV6_SUPPORT - the phone has IPv6 support (https://en.wikipedia.org/wiki/IPv6)
• LABEL_ADJUSTABLE_BACKLIGHT - if the phone has a label display: the backlight can be adjusted in steps (not just on/off)
• ORDER_CANCEL_LEFT_OK_RIGHT - is the CANCEL key on the left and OK key on the right of the navigation keys or the other way around

Example code: show a checkbox which is ticked if the corresponding feature is available

<?xml version="1.0" encoding="UTF-8"?>
<SnomIPPhoneText>
    <Text>
        $(x_o:$(show_feature:FEATURE_PUI_STYLE_SIO)) FEATURE_PUI_STYLE_SIO<br/>
        $(x_o:$(show_feature:FEATURE_SMART_LABEL)) FEATURE_SMART_LABEL<br/>
		$(x_o:$(show_feature:FEATURE_SECOND_DISPLAY)) FEATURE_SECOND_DISPLAY<br/>
    </Text>
</SnomIPPhoneText>

Result on Snom D375:

Result on Snom D745:

Result on Snom D385:

Result on Snom D735: