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 patchcord. The pigtail is usually fusion spliced to an optical fibre of an external cable; and the patchcord 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 inner part with a precision alignment mechanism; which is made to demanding specifications. The alignment sleeve and precision body ensures: reliable, long term, mechanical and optical performance for the through adaptor. The through adaptor is capable of a reasonable number (eg 500) of matings/unmatings, and of withstanding normal (not excessive) handling forces/loads without suffering any damage or 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.