Thermal Printer - pos command to beep

Since you did not specify a specific thermal printer, I'll have to speak generally. In general, thermal printers use beeps as error codes. Therefore, they do not provide a way for the drivers to make them beep for other reasons. Further, it seems like a poor requirement, since it will be self-evident that the printer has printed a new order since the printed order will spit out of the printer.

My recommendation would be to re-evaluate your requirements. If it is absolutely necessary to alert the users through an audio format when a new order has printed, do it through the computer. The computer can send any number of sounds quite easily. For instance, you could record a "The printer has a new order" message that gets played whenever the printer prints something. Unfortunately, this does mean that the computer needs to be nearby and have speakers. If the computer cannot have speakers but is nearby, you can use the internal beep option to make a simple beep.