Image 1. Positive centre tip.
Image 2. Negative centre tip.
When selecting a suitable switch-mode power supply adapter for your electrical devices you must ensure the polarity is compatible. For example power adapter plugs can have a positive or negative centre / tip. The Bush Australia model BR25DAB radio power adapter has a positive centre / tip. You can usually find out which centre tip power adapter type your device has by looking at the rear specifications. Furthermore it will display a universal polarity image for identification. For instance the DAB Bush Australia radio lists the specifications as such above image.