| 摘要 |
An apparatus (12) is provided for use in determining a length at least representative of the length of a tube that defines a passage in an optical fibre cable (10) along which an optical fibre unit can be installed by blowing. The apparatus (12) comprises a pressure reservoir (32) in which a gas at a known pressure can be stored, outlet piping (34) connected with the pressure reservoir (32) and having an outlet end spaced from the reservoir for connection to a tube of the optical fibre cable (10). The apparatus has a pressure detecting arrangement (42) for detecting gas pressure in a tube connected with the outlet end of the outlet piping (34). In use, the gas stored in the pressure reservoir (32) is released into the tube and knowing the pressure of the gas when stored in the pressure reservoir, the volume of the reservoir and the pressure of gas in the tube after release of the gas from the pressure reservoir, it is possible to determine the volume of the passage defined by the tube and knowing that volume, it is possible to determine the length of the tube.
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