hi don . you may not believe this, but sonobouys was an afterthought, during ww2. circut boards and hydraphones were new technology buding back then , but you can try motorola they were the people that i got my bouys from, try during my p-3 days, try motorola defence sys , thay can be quite helpfull or carl smith capt , usnr reserve officers assn , @304 594 2331