From our point of view (in-house) blue line implies skinning the transducer with PVC film (Polyvynylchlorid).

At the beginning of the 90s when we were authorised repair shop of Microtech Gefell GmbH (former VEB MTG) we had self-produced PVC diaphragm. We have retained (at that time self-innovated) blue line for PVC and red line for Polyster/Carbonat although we had shuted down the production of PVC diaphragm because of decreasing demand and the trend to polyester.

Is seems that PVC diaphragm has gained more attention by recontemplating to „vintage“. Because of increasing of interest in mentioned film we have resumed PVC in our offer.

blue line

Transducer skinned with PVC film will be signified by blue line.