If you become legally liable to pay damages in respect of loss of or damage to property arising out of the failure of any alarm system security system or security device sold supplied or maintained by you or which forms part of any work that you have completed to perform as intended or expected cover is provided subject to the following:

a) the maximum amount we will pay for all such claims during the period of insurance is as shown in the schedule

b) you shall pay 10% in respect of each claim provided always that such amount payable by you in respect of each claim shall not be less than £500.