A wireless pocket transmitter having a rear side, a front side and a receiving compartment for a rechargeable battery. The receiving compartment has a rear wall which at least partially forms a part of the rear side, two side surfaces and a connecting portion with electrical contacts. The two side surfaces are each coupled with a first side to the rear wall and with a first end to the connecting portion. The second ends of the side surfaces each have a respective guide for the battery. The guides do not extend along the entire length of the side surface and the guide has two projections and a passage therebetween.