DS-KD8003-IME2 speaker makes noise all the time

Hello!

I installed my intercom system this weekend with:

• DS-KH6320-WTE2
• DS-KD8003-IME2
• DS-KAD706

all works fine. But the outdoor station is making noise all the time with the speaker. Like a interference signal in the 90s. This is a good example: Electric Buzzing Steady its not very loud. with the cars on the road you can't here it. but in the evening with 10 cm between your ear and the KD8003 you...

DS-KD8003-IME2 speaker makes noise all the time