54 are optional features in the present device and merely make its operation respond without concern for a residual count in the counting means 32 the conductors 41 42 and 51 supply the basic inputs to the condition control operating means 50 the condition control operating means 50 has been shown as capable of controlling two heating stages and two cooling stages by means of simple digital logic which includes a number of and gates or gates a not gate and a group of c d flip flops the digital logic contained in the condition control operating means 50 can be varied extensively depending on the type of staging required and whether the staging is for one type of control such as heat only or for dual type staging of both heating and cooling in connection with fig1 a simple digital arrangement of logic will be specifically disclosed that is capable of turning 34 on 34 a first stage of heat and time proportionally modulating that stage of heat the system will also be capable of then energizing a second stage of heat and returning to the first stage of heat for additional time proportional modulated operation any number of additional stages of heat could be added but have not been shown the logic disclosed in the condition control operating means 50 further allows for the addition of two stages of cooling when the cooling operation is called for the digital logic also includes a cooling set point above heating offset thereby creating a differential between the heating and cooling stages of operation this will be described in some detail in.