Features Compact 12V 250mA double gang power supply unit Can provide power up to two NC944 four zone call controllers Suitable for use in many other applications Optional NC941B 12V 0.3Ahr battery back-up kit also available to ensure the NC930 remains operational in the event of mains failure Mounts on a standard UK 25mm double gang flush or surface back box. Please contact customer service on [email removed by eBay] with details of product for more information. Every hire comes with a weekly or monthly supply of accessories on discount.