f. Dielectric Strength: Insulation between conductors capable of withstanding 700 volt instanta- neous A.C. test potential for two seconds. Insulation between conductors and sheath capable of withstanding 1400 volt maximum instantaneous A.C. test potential. . Lt shall be equal and similar to Western Electric Type D.S.A. 17-17. It shall be spun to messenger with .091" 0O.D. 17-18. Underground telephone pairs, unless otherwise 17-19. Minimum cover for underground telephone pairs lashing wire. indicated, shall be #17 A.W.G. duplex, equal to Whitney Blake #17TBPR. similar and shall be two feet zero inches unless otherwise approved. Trench depths shall be increased as required at crossovers to provide a minimum separation between telephones and power or coaxial cables of one foot zero inches. Underground telephone pairs shall be installed in same trench with underground control and signal cable where closely adjacent parallel runs are indicated on the plans. Trenching, backfilling, etc., shall conform to applicable provisions of "Earthwork for Utilities” Section of these specifications. 17-20. The location of all underground telephone cable shall be adequately identified by posts marking the presence of these lines. PUBLIC ADDRESS SYSTEMS: 17-21. Outside voice paging systems shall be provided in accordance with the following specifications and installed as shown on the drawings. 17-22. The equipment shall operate from 115 volt, 60 eycle power source. It shall be designed to withstand tropical weather and ruggedly constructed. 17-23. Each Control Console shall be housed in an aluminum turret (RCA type MI-14909 or equal) approxinately 22" wide, 11" high, and 16" deep. The panel shall contain a volume indicator meter, a volume control device, and an on-and-off switch with a red bulls eye. It shall have five lever action four pole switches; one each to handle the switching of relay current , 17-3