The through connector (or adaptor) is mounted in a patch panel, of an optical fibre termination unit, or OFDF, and allows a pigtail to be connected to a patch cord. The pigtail is usually fusion spliced to an optical fibre of an external cable, and the patch cord connects to transmission equipment. A through connector allows the optical transmission system connection to be quickly made and broken, as required. This enables fault finding and maintenance activities (such as service restorations & rearrangements) to be undertaken quickly and efficiently. The SC connector is a compact size unit. The adaptor unit comprises a plastic body and the inner part with a precision alignment mechanism; which is made to demanding specifications. The alignment sleeve and precision body ensure reliable, long-term, mechanical and optical performance for the through the adaptor. The through adaptor is capable of a reasonable number (e.g. 500) of matings/unmatings, and of withstanding normal (not excessive) handling forces/loads without suffering any damage or a significant increase in optical performance. The assembly is capable of reliable operation in Exchanges or Repeaters over the temperature range of ‐25 degrees to + 70 degrees Celsius, and up to high levels of RH. Two way and four-way through connector modules are also available. The phosphor bronze through connector is typically used on multi‐mode systems.