An electrical connector includes a plug that mates with a receptacle. In a medical application, the plug is connected to electrical leads that pass through a patient's skin to an implanted medical device in the patient's body, while the receptacle is connected to external medical equipment. All electrical contacts in the plug are on internal portions. The receptacle includes annular contacts that contact the internal electrical contacts on the plug when the plug and receptacle are properly mated. The receptacle includes a plurality of annular electrical contacts that have a first diameter and are separated by a plurality of annular insulators having a second diameter smaller than the first diameter.