Receptor: 1. In cell biology, a structure on the surface of a cell (or inside a cell) that selectively receives and binds a specific substance. There are many receptors.
The most common is EPNS (Electro Plated Nickel Silver) but many other symbols are used: 1  EPBM (Electro Plated Britannia Metal). 2  EPCA (Electro Plated Copper Alloy). 3  ESM (Electro Plated Silver Mounts).he most common is EPNS (Electro Plated Nickel Silver) but many other symbols are used: 1  EPBM (Electro Plated Britannia Metal). 2  EPCA (Electro Plated Copper Alloy). 3  ESM (Electro Plated Silver Mounts).
Now, one of the old guys! In PLC work NPN means the sensor or switch connects to the negative of the power supply. When the sensor is made up it connects the plc input to the negative and makes up the PLC input point. The PNP is the same except it connects the PLC input to the positive side of the supply. In most of my plc work we use NPN type sensors.