1、INTERNATIONAL TELECOMMUNICATION UNION)45G134 2 TELECOMMUNICATIONSTANDARDIZATION SECTOROF ITU4%,%2!0(94%,%2!0(G0G042!.3-)33)/.2%3%26%G0G0#(!%,3G0G0 amended at Geneva, 1964)The CCITT,consideringthat it is desirable that maintenance measurements on the channels of international voice-frequency telegrap
2、h(VFT) systems should disturb communications as little as possible,unanimously declares the view(1) that, whenever possible, measurements on a working channel of a VFT system should be carried out onlyafter the channel concerned has, if necessary, been replaced by a spare channel;(2) and to this end, the CCITT considers that it is desirable that one channel should be reserved for thispurpose in each VFT system.(3) When this change is not possible, the channel user will be informed in advance that measurements or testsare about to be carried out on his circuit.
