Motorcycle helmet communications cables connecting substantially all models of cellular telephones to a "CHATTERBOX" HJC-GMRS X1 rider-to-rider motorcycle helmet communication system. A length of audio cable is provided with a 3.5 mm stereo plug at one end designed to engage the auxiliary input jack of the motorcycle helmet communication system. At the second end of the cable a 2.5 mm stereo plug is provided for engagement with the hands-free outlet of any cellular telephone. The first plug includes four co-axial contacts for engaging contacts within the auxiliary-input jack of the communication system. The second plug has only three co-axial contacts for engaging contacts in the hands-free jack of most cellular telephones. The internal wire connections between the contacts of the first plug and the contacts of the second plug are selected to enable most cellular phones with hands-free jacks to operate with the HJC-GMRS X1 rider-to-rider motorcycle helmet communication system.