the idea is like this,
most of the kitchen POS receipt printer doesn't provide function "beep" after printing out receipt, some OEM china provides this beep function.

most restaurant in f&b industries use those commercial software, no way they could wish /request a beep feature easily (even if the receipt printer got beep control code).

what i suggest is,

a device ( that enable LAN cable in & out *assume they are network or using print server ) with a small speaker with volume control to beep whenever a series of network print data (eg, start printing control code) was detected / pass through.

because kitchen is a noisy place,
a series of beeps might catch the workers attention to proceed the customer order.

i just feel edfed could make this device

how bout an order of 100 unit?

i don't think the beep is so needed.
when you print, you basically wait for the end of the print.

technically, it would be really hard to design.
first problem is the power supply (pick it on the network???)
second is the way to analyse the network activity (what would be the end of print frame?)
third would be to do it without a huge bench of various printers to test. (does it work on every models of printers?

a beep (or any other signal) from the computer responsible of the print isn't enough?

well, the beep is so needed because while the chef is doing his work, 2 or 3 more orders might come, so if some how a beep sound was created, the chef will get notified, and maybe cook faster or speed up in somehow.

otherwise the chef need to glance on the printer once in a while to see if there is order or no.

power supply, maybe an AA battery? or computer motherboard battery?

network activity,
idk if Windows will from time to time ping the printer or not, if let say, windows will only transmit data when there occur some printing, then we could see if we detect signals then beep.

third, we need a hardware like below, should works on every printer
lan cable in -------> our beep device ----> lan cable out ----> to print server / printer ethernet port

they usually put the PC at counter, link multiple receipt printers (eg, food dept, beverage dept, chinese food dept and etc) with network cable.

and what about a sort of detector that simply detect the presence of a printed paper? it would be really simpler to find.

hi edfed,
there are several ways, imo,

1. we can detect if paper coming out from the receipt printer, maybe a string or laser or etc etc that could detect the presence of paper coming out. (like you said) then we beep

2. since the printer will shake when printing, if we could paste the shake sensor on the printer, then beep when we feel shake, might be a good way.

3. or a sound detector (micro microphone?), since printing will cause some changes in environment sound for dot matrix based, (thermal got a cutter sound), we could detect such high volume sound then beep.

or any others ways? what u think?

You could detect led light flashing on printer or ethernet.

a power consumption detector also.
when the printer is idle, it would consume far less energy that when it is working...

maybe the shaking induced by the print would be fine to detect, but it will also detect the earthquakes and other vibrations.

i think the photosensor is a good deal, but the power detector can be good too. after that, what would be the less expensive to produce, and the more accurate???
it is a huge question for a very basic problem.

yeah, huge question for basic problem
human is so creative

Maybe the printer can print a row of ------- to make a buzz?

>and maybe cook faster or speed up in somehow.
Have you ever worked in a kitchen? Cookie works at his own pace