circular cavity 22 and to an arcuate opening 25 therein adapted to receive an arcuate portion 40 formed on insert member 20 it will be understood that the invention is not limited to such shapes but that cavity 22 may also be e g square or rectangular in shape and that opening 25 and section 40 may also suitably be of other shapes e g square rectangular or triangular also it will be understood that the invention is not limited to an insert member which is removably fixedly mounted in place in the angle cap housing as the diaphragm and clamp member may be formed as an integral extension of the front portion of the wiring chamber cavity wall with equally satisfactory results while it also will be understood from the foregoing description that neither the angle cap housing nor the cable clamp and diaphragm insert member of the invention are in any way limited to the use of particular materials they are preferably formed from molded thermoplastic resin materials with respect to the materials from which each of the angle cap body and insert members are formed certain injection moldable thermoplastic resin materials have been found to produce highly satisfactory results and are given as an example of the preferred mode of carrying out the invention from which other equivalent materials will be apparent to those of ordinary skill in the art thus it has been found that the polycarbonate resin material sold by the general electric company under the trade name 34 lexan 34 grades 103 or 123 is a particularly preferred material for the angle cap body from the standpoint of strength and high temperature resistance.