Plain Old Telephone Service 
Plain Old Telephone System 
Parents Over The Shoulder 
Pat On The Shoulder 
Plain Old Telephone Services 
Pretty Old Tired Stuff 
Panel Operator Training Simulator 
Pan-only Triangulation System 
Plain Old Telephone Set 
Plain Old Time Sharing 
Plain Old Time-Sharing 
Plain Ordinary Telephone System 
Point Of Termination Station 
Portable Optical Tracking Station 
postural orthostatic tachycardia syndr… 
postural tachycardia syndrome 
Pretty Old Time Stuff 
Publicly owned treatment system 
Purchase Of Telecommunications Service…