Ding dong.

Where can we get an electronic door bell that doesn't get confused by other electronic signals.  For instance, when we turn on the caravan alarm the house door bell sometimes goes off - as does our dog.  When you press the doorbell it often (usually) doesn't work.  This is the second system we've had, it was from B & Q and, like the first system, was made in China (although you couldn't tell this until it was unpacked.).  We want a British, or possibly EU, doorbell on the theory that it will have a frequency that doesn't interfere with, or get interfered by, other electronic signals.  Any suggestions.