A medium-haul carrier telephone system

IN THE LAST 30 years the rise of dialing requirements for local and long distance circuits, coupled with increased plant construction costs, has made the older types of carrier telephone systems obsolescent. It was found that there is a distinct field for medium-haul carrier telephone systems, capable of transmitting up to about 12 decibels above, and receiving down to about 15 decibels below, the level at the switchboard at the transmitting end, and providing circuits with 2-wire net circuit losses of two to six decibels. Such a system should transmit voice frequencies from about 300 to 2,700 cycles with a rather flat characteristic. The modulator and demodulator carrier oscillators should be stable to about three cycles to permit use of voice-frequency carrier telegraph systems.