The present invention relates to opto-electric switch comprising of light source (LED) and light receiver (photodiode) fixed in  cylindrical PVC tube; employing optical transmission means for detecting the presence or absence of liquid and liquid level monitoring;  LED for status display of presence or absence of liquid; potential-free relay contact for alarm/control 1 action. The opto-electric switch is  disclosed in two design variants, one sideltop mount type and another inline mount type with integrated electronics. The opto-electric  switch can be used for detecting the presence or absence of liquid for example, in process pipe lines and also for sensing liquid level,  for exaiiple, in process vessels.