Testing apparatus for transmission system

Claim 1

A testing apparatus for a transmission system comprising: a test pattern insertion unit, connected to an input of a transmission system to be tested, for transmitting test signals in a test pattern having a repeating cycle to the transmission system; a test pattern confirmation unit, connected to an output of the transmission system, for inspecting said test signals passing through the transmission system and discriminating whether or not the test pattern was normally received; and a non-test pattern followup unit, connected to the input of the transmission system, for sending to said transmission system a non-test pattern that is different from the test pattern for a predetermined time following an end of issuance of the test pattern from the test pattern insertion unit, said predetermined time being approximately equal to a cycle of said repeating test cycle, said transmission system being substantially cleared of said test pattern by sending said non-test pattern for said predetermined time, wherein said non-test pattern follow-up unit comprises a test command unit, a non-test pattern generator for outputting said non-test pattern on the basis of a test finish command from said test command unit commanding the start and end of testing by said testing apparatus, and a timer unit coupled to said test command unit for controlling the transmission of said non-test pattern for said predetermined time; said testing apparatus further comprising: a first selector, coupled to said transmission system, for selecting inputting to said transmission system said test pattern and said non-test pattern in place of main transmission signals during a test period from when a test start command is output from said test command unit to when said predetermined time has elapsed from the output of said test finish command, and a second selector for connecting an output of the transmission system to an input of said test pattern confirmation unit instead of an input side of said main transmission signals to be output from said transmission system during said test period, said non-test pattern follow-up unit including a third selector for selectively switching between an output from the test pattern insertion unit and an output from said non-test pattern generator and applying the output from said non-test pattern generator to the first selector, and said third selector selects one of the output of said test pattern insertion unit in response to said test start command from said test command unit and the output of the non-test pattern generator in response to said test finish signal from said test command unit.