These include: improved lightning damage protection for exchange equipment;installation of standby generators at all our exchange sites to ensure service continuity in the event of disruption to the public electricity supply;introduction of power filters to eradicate failures due to mains electricity supply problems;provision of alternative call routing, where possible, from the local exchange into the national network;development of methods to reprogram an exchange, and to enable interception of 999 calls under exchange isolation conditions;satellite telephones, ready for immediate deployment, to enable communication from the isolated exchange under major failure conditions;introduction of an arrangement whereby BT can use a helicopter to deliver personnel and equipment to site; andmobile exchanges and ancillary equipment on permanent stand-by, to be deployed in the event of catastrophic failure.