How can I switch off the infrared interface on the Metrahit multimeter?

First of all, general information on the irStb parameter. The irStb parameter has the following meaning:

• Parameter irStb=on means that the device can be switched on by an external request via the IR interface when it is switched off. The device is therefore in a kind of stand-by mode.
• Parameter irStb=off means that the device cannot be switched on by an external request via the IR interface when it is switched off. It is completely switched off.
• When switched on, communication via the IR interface is always possible. Regardless of whether the irStb parameter is set to on or off.
• Regarding the IR interface control indicator in the display: This should disappear if parameter irStb=off and be shown if parameter irStb=off. This applies equally whether the device is switched on or off. If this does not happen, it would be a (small) bug in the signaling.

Given the above information, the question of how the IF interface can be switched off can be answered as follows: When the device is switched on, it cannot be switched off at all. When the device is switched off, it is deactivated if the parameter irStb=off has been set beforehand.