KP04 & DP03 fitted back to back

[michaelmike]

The KP04 & DP03  were fitted back to back on a 30cm deep brick wall. When operated they produce a loud whistle each time a person talks to either end. Note that when using the second KP04 fitted upstairs operation is perfect. Tried adjusting the pots on Comfort DP and DP03. This minimises the effect but the visitor cannot be heart over KP04. Used screaned alarm cable for the installation. Both KP04 & DP03 wires run along the same conduit and through the KP04 wall metal box.

Would the usage of aluminium foil tape, fitted at the back of each units housing, solve the problem? Is there anything else that could be done to solve the problem?

Is there anything else to be done to solve the problem? 

[slychiu]

The whistling sound that you describe is due to positive feedback between the speaker of one and the microphone of the other. This is similar to the effect during a live performance where the microphone and speaker are too close to each other and the gain is turned up too loud

The solution is to move the keypad and door station further away from each other. Screening the cables will not held because it is the sound feedback which is the cause. You can also try to reduce the volume of both speakers to reduce the effect but it is best to move the two units apart

[michaelmike]

Thank you Chiu. That I have had in mind as the last solution, hoping that there might be another solution. It seems to be innavitable to move the two further appart from each other. So it will be done.

Thank you again.

Mike