DH100 Information
AUTO POWER OFF
After 5 to 6 minutes of not using the horn the unit will automatically shut down. This is to preserve the batteries. Just turn it off and then on again to continue use.
AC ADAPTOR
The correct part, from Casio, is the AD-1 AC adaptor. This is a country specific part! The Horn is protected from the wrong polarity, but the correct polarity is "negative in the centre".
The AC adaptor is rated 7.5 volts at 600 mA. Most universal AC adaptors that have a 7.5 volt output and at least this much current will work just fine. I don't recommend using 9 volts as some have on the internet. I am not sure how much voltage the regulators can handle, but I do know that if you damage the regulator you are out of luck because they are not made any longer and not available anywhere. *
WARNING
The manual says "Don't blow into the horn during switch on".
The reason you don't blow on the horn during power up is this: On power-up, the horn calibrates the breath circuit by measuring the value of the pressure sensor to determine what 'no breath' looks like. It has to do this because pressure sensors tend to be sensitive to things other than pressure, notably temperature. You can demonstrate this by sucking on the horn during power-up, introducing a 'negative' pressure. Then when you stop sucking, the horn will start playing, even with no breath applied. Or you can blow gently on the horn during power-up. Then the horn won't sound until you blow harder than you did on power-up. Turning the horn off and then on restores it to normal operation. No damage will occur. *
* Information kindly sent by Ted Keys.