We expect the monopole signal at the lowest frequencies below $100\. $MHz to be composed to two components: the deep Rayleigh-Jeans tail of the cosmic microwave background and two distinct features: the dark ages trough at $\sim 17\. $MHz and the cosmic dawn trough at $\sim 75\. $Mhz. https://allfixelectricales.shop/product-category/pressure-switch/