. The Bell System technical journal . 120-kc. carrier. Assembly The different panel units which make up the terminal of a typeK system are assembled on a functional basis with similar panels ofother K systems, the channel modulator-demodulator panels in one A CARRIER TELEPHONE SYSTEM FOR TOLL CABLES 101 bay, the carrier supply in a second, the group modulator and demodu-lator in a third, etc. The compactness of the equipment makes itpossible to mount the modulators and demodulators for 18 channelson one 11 ft. 6 in. bay 19 inches wide. Signaling The same type of ringdown signaling equipment is
. The Bell System technical journal . 120-kc. carrier. Assembly The different panel units which make up the terminal of a typeK system are assembled on a functional basis with similar panels ofother K systems, the channel modulator-demodulator panels in one A CARRIER TELEPHONE SYSTEM FOR TOLL CABLES 101 bay, the carrier supply in a second, the group modulator and demodu-lator in a third, etc. The compactness of the equipment makes itpossible to mount the modulators and demodulators for 18 channelson one 11 ft. 6 in. bay 19 inches wide. Signaling The same type of ringdown signaling equipment is used with thechannels of this system as with the voice-frequency toll circuits. A1000-cycle tone, interrupted 20 times per second, is impressed on achannel terminal, modulated, and transmitted over the carrier systemin the allotted channel band. At the far end, it is demodulated tooperate the receiving end of the standard voice-frequency signalingcircuit, or to be transmitted along an extended voice-frequency circuitto its Fig. 18—Vacuum lube test set. Telegraph and Program Applications Voice-frequency telegraph can be superimposed on any of the carrierchannels as is now done on the three-channel open-wire is being developed to include a program channel on thecable carrier system. This will be done by devoting to the programcircuit the frequency space occupied by two of the 4-kc. speech bands. 102 BELL SYSTEM TECHNICAL JOURNAL System MaintenanceArrangements are provided whereby the tubes may be tested on aroutine basis as has been done in voice-frequency practice. Theamplifier panels, however, are provided with test jacks which are con-
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