ข้อมูลสัญลักษณ์จำแนกการออกแบบผลิตภัณฑ์ระหว่างประเทศ


รหัส / code คำอธิบาย / code name Version
H04M0001738000 Interface circuits for coupling substations to external telephone lines (H04M0001780000 takes precedence);; 1
H04M0001740000 with means for reducing interference; with means for reducing effects due to line faults 1
H04M0001760000 Compensating for differences in line impedance 1
H04M0001780000 Circuit arrangements in which low-frequency speech signals proceed in one direction on the line, while speech signals proceeding in the other direction on the line are modulated on a high-frequency carrier signal 1
H04M0001800000 Telephone line holding circuits 1
H04M0001820000 Line monitoring circuits for call progress or status discrimination 1
H04M0003000000 Automatic or semi-automatic exchanges 1
H04M0003020000 Calling substations, e.g. by ringing (selective calling H04Q) 1
H04M0003040000 the calling signal being supplied from the final selector 1
H04M0003060000 the calling signal being supplied from the subscriber's line circuit 1
H04M0003080000 Indicating faults in circuits or apparatus 1
H04M0003100000 Providing fault- or trouble-signals 1
H04M0003120000 Marking faulty circuits "busy"; Enabling equipment to disengage itself from faulty circuits 1
H04M0003140000 Signalling existence of persistent "off-hook" condition 1
H04M0003160000 with lock-out or secrecy provision in party-line systems 1