sentences:  Currently only West Midlands Ambulance Service offers a paramedic on every ambulance.The majority of emergency medical personnel are employed by the public ambulance services of the National Health Service and respond to emergency calls generated by the 999 system.Many are also employed by private ambulance companies and voluntary aid societies such as the British Red Cross and St. John Ambulance, who provide services such as event medical cover or support to some NHS ambulance services in times of need or under contract.