Conversion of a VHF communications system from standard to tone squelch

This paper describes the original VHF mobile radio system in the Indiana and Michigan Electric (I&ME) Company and how it operated with standard squelch. It points out some of the problems which were encountered at the relatively low operating frequency in the 37-MHz region and goes on to show the solution for most of these problems by converting the entire system of 19 base stations and 300 mobile units from standard squelch to a tone coded squelch. The entire changeover was done in an economical manner and without disrupting operation of the original system while the conversion was being made. The benefits ensuing from this conversion are covered in detail.