Labels:box | door | earth | sky | windowpane OCR: To the 2-wire To the 4-wire circuit circuit CO CCITT 49310 CCITT. 49320 receiving pari sendina part coupling revice te.g. hybrid set of directional filters etc.] FIGURF 16/0.451 FIGURE 17/Q.451 Four-wire multifrequency signalling equipment Tno-wire muhifreguensy signalling cuuinment receiv sending direct tional mulifreguensy cquipment
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