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I'm reading an outline of spurious emission test for Bluetooth devices which states that

The Equipment Under Test (EUT), a Bluetooth module is switched to a test nullmode in which it generates the transmitter signal required for the test.

Does that mean all Bluetooth devices from toys to speakers need to implement a separate, specific test mode for the spurious emission test even if they incorporate a certified Bluetooth module? From my understanding, this test mode enables loop back mode which may not be pertinent to the actual normal operation of the device, ie most devices don't utilise loop back mode.

In fact, how is this test mode triggered in the test lab? Must the device itself need to be able to switch to test mode given a certain packet?

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This test mode is initiated using a special AT command, just like the other AT commands sent to the module (I only have experience working using the AT command method of controlling a Bluetooth modem; I've never used the HCI -- Host Controller Interface -- layer, but I'm sure there is an equivalent method of entering this mode).

If I recall (it's been a couple of years since I've done this) the command lets you specify a channel frequency and power level (typically maximum level is used), and puts the transmitter into a state where it is continuously transmitting alternating 0's and 1's. There is no connection made to another Bluetooth device. This testing is typically done inside an anechoic chamber, so it doesn't interfere with anything.

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