Bell Telephone Laboratories

Barry Sheldon Bosik

Dale Eugene Stone

Frank P Tuhy, Jr

Tadikonda N Rao

Jeffrey H Derby

A bilateral repeater for communication transmission lines is described in which the opposite directions of transmission are separated by frequency bands for amplification. The repeater is powered from a power conversion unit energized from the line potential. The repeater includes three-electrode gas tube breakdown devices connected across the repeater for each conductor of the transmission line. The third electrodes in the gas tubes are cross-connected together with no ground connection.

Repeater overload circuit

A ringing signal generator is disclosed for remotely generating telephone ringing signals having a trapezoidal waveform. A single capacitor and two constant current sources control the wave shape while current limiting is provided on both the positive going and negative going half-cycles of the ringing signal. A voltage offset is provided between the ringing signal source and the subscriber line to prevent loading the ringing signal with the subscriber line feed circuit.

Ringing generator

A ring trip detection circuit is disclosed for a remotely generated ringing signal in a subscriber loop carrier system. The ring trip detection circuit is enabled only during the high voltage half-cycle of the ringing signal to increase ring trip detection sensitivity and reduce the size and complexity of the ring trip detection circuit.

Ring trip detector circuit

A subscriber loop carrier system is disclosed for frequency multiplexing a plurality of subscriber channels on a single twisted metallic pair using frequency division techniques. Supervisory signaling is accomplished from the central office to a remote location by imposing a signaling tone of the carrier frequency for each signal. Supervision from the remote terminal to the central office is accomplished by interrupting the carrier signal itself. Ringing signals are supplied by interrupting the tone signal at a 20 Hz rate. Testing the subscriber channel is accomplished by leaving the tone on for a period in excess of the period used for ringing. Each channel of the carrier system can, therefore, be independently tested by using the uninterrupted tone to gate the remote carrier on for transmission back to the central office terminal. When detected, this carrier signal from the remote terminal indicates a complete communication path from the central office to the remote terminal and back again, i.e., channel continuity.

Loopback test system

A line feed circuit for a telephone subscriber loop is disclosed which can be used to supply constant current to the subscriber loop. An operational amplifier, operating in its direct current mode, is used to maintain the current constant. The same operational amplifier, operating in its alternating current mode, magnifies the value of a capacitance bypassing the line feed circuit. In this way the alternating current impedance of the line feed circuit is maintained at a very low level.

Line feed circuit

A variable delay ringing detector in a single channel carrier system for telephone service is disclosed including at the remote terminal a battery charger for charging a battery which powers the carrier electronics at the remote terminal. A ringing generator and supervisory circuits are disclosed to provide normal telephone supervision on the carrier-derived channel. The variable delay ringing detector includes two capacitors which are charged in response to ringing current.

Variable delay ringing detector

A single channel carrier system for telephone service is disclosed including a remote terminal having a ringing generator included therein for generating ringing signals to operate the ringers of remote subscribers. The ringing generator is a dc-to-dc converter for stepping up a battery voltage to ringing voltage lvel that is interrupted at a 20 Hz rate. The generation of ringing signals is controlled by a carrier signal interrupted at a ringing rate. Detection of the ringing signals on the carrier utilizes a delay circuit to prevent response to inadvertent signals as well as delay hysteresis to ensure the bridging of detection from one 20 Hz cycle to the next. The ringing generator must also be regulated, both in current and in voltage, to prevent danger to personnel, damage to equipment, and excessive power consumption.

Voltage and current controlled converter for telephone ringing

A single channel carrier system for telephone service is disclosed including at the remote terminal a battery charger for charging a battery which powers the carrier electronics at the remote terminal. A ringing generator and supervisory circuits are disclosed to provide normal telephone supervison on the carrier-derived channel. The battery charger includes a dc-to-dc converter to increase the rate of battery charging and an interface unit to minimize the effect on the telephone line by the charger. In one embodiment, the interface unit disconnects the charger to permit leakage testing of the line.

Battery charging circuit

A single channel carrier system for telephone service is disclosed including a remote terminal having a ringing generator included therein for generating ringing signals to operate the ringers of remote subscribers. The ringing generator is a dc-to-dc converter for stepping up a battery voltage to ringing voltage level that is interrupted at a 20 Hz rate. The generation of ringing signals is controlled by a carrier signal interrupted at a ringing rate. Detection of the ringing signals on the carrier utilizes a delay circuit to prevent response to inadvertent signals as well as delay hysteresis to ensure the bridging of detection from one 20 Hz cycle to the next. The ringing generator must also be regulated, both in current and in voltage, to prevent danger to personnel, damage to equipment, and excessive power consumption.

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Parsippany, NJ, United States of America

Barry Sheldon Bosik