Refer typical diagram of ASPL Auto change over unit where filled cylinders in Bank- A and Bank- B connected to inlet of Auto change over regulator.
In first stage regulator of auto changeover unit fixed amount of gas pressure will be controlled and in second stage means line regulator will be adjusted with knob to achieve desire system pressure of gas. This two-stage pressure regulation shrinks the supply pressure effect caused by depleting gas cylinders.
During operation when Gas supply Bank-A pressure reduced to Predefined level then it will auto changeover to Bank-B to continue supply of gas. Empty cylinders of Bank-A can be taken for refilling.
Refer to the datasheet for more details