Small, battery operated RF transmitter for portable audio devices for use with headphones with RF receiver

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to FIG.
1, there is shown a diagram of a system within the genus of the invention.
A battery operated audio source 10, typically a portable stereo radio, a portable cassette player or a portable compact disk player, generates audio signals from received radio signals or program material recorded on a medium.
These audio signals are presented at a headphone or output jack 12.
A portable, battery operated RF transmitter 14, comprised of a transmitter housing 16 and enclosed integrated circuitry and a male plug 18, which plugs into the headphone or output jack 12.
The audio signals generated by the audio source 10 are amplified and modulate an RF carrier.
The RF carrier is coupled into an antenna for radiation to a headphone receiver 20.
The antenna for the RF transmitter 14 is comprised of the ground circuit of the RF transmitter as one half of a dipole and the ground circuit and other conductive components of the housing of the portable audio source 10 as the other half of a dipole.
A dipole antenna as used herein includes any antenna having two radiating elements.
The headphone set 20 has a built in radio receiver 22 with a small rod antenna 24.
The radio receiver 22 has an audio output which is coupled to two earphone pieces 26 and 28 which are held adjacent a wearer's ears by frame 30.
The advantage of the above described system is that there are no wires that couple the audio source to the headphones.
This prevents the user from possibly snagging the wires on his or her arms during exercise or physical work and prevents the user from catching the wires on weightlifting equipment in use by the user or items the user is walking by.
Catching the wires can not only damage the audio source and headphones by causing them to be dragged from the user's body and dropped from a distance onto a hard floor, but also presents a potential safety hazard.
Note that there is no external antenna whip or rod on RF transmitter 14.
This is a handy feature since the audio source is often worn on the user's beltline, so a whip antenna sticking up further than the transmitter 14 itself could poke the user in the side and would be susceptible to bending or breakage by active users who are moving around