Bell Telephone Laboratories

At&t Bell Laboratories

American Telephone & Telegraph Co., At&t Bell Laboratories

William F MacPherson

Peter W Shackle

James A Davis

Harry E Mussman

Adrian R Hartman

James E Kohl

Robert S Scott

Terence J Riley

Charles H Sharpless

Charles Elmer Jones, Jr

Raymond M Bulley

Robert F Youhas

Irving M McNair, Jr

Robert C Hudson

To switch a first gated diode switch (GDSL1) to the 'OFF' state requires a voltage applied to the gate which is more positive than that of the anode or cathode and a sourcing of current into the gate of substantially the same order of magnitude as flows between the anode and cathode of the first switch. Control circuitry, which uses a second gated diode switch (GDSC) coupled by the cathode to the gate of the first switch (GDSL1), is used to control the state of the first switch (GDSL1). The control circuitry also comprises a first branch circuit coupled to the anode of the GDSC and to a first potential source V1 and a second branch circuit coupled to the anode of GDSC and to a second potential source V2 which is of a lower potential than V1. The second branch circuit has a high voltage and high current capability switch in series between V2 and the anode of GDSC. The first branch circuit has a high voltage but modest current handling switch in series between V1 and the anode of GDSC. The second branch circuit is used to provide a surge of current if and when needed during the current break operation to turn GDSL1 to an OFF state and the first branch circuit is used to maintain the state of the load switch. The second branch circuit can be shared by many control circuits.

Control circuitry using two branch circuits for high voltage solid-state

A floating battery feed circuit comprising a switching-mode, flyback power converter wherein a capacitor connected to a converter transformer winding develops a relatively low voltage used to energize the converter control circuitry. The converter control circuitry prevents the operation of the battery feed circuit unless the voltage developed by the capacitor is above a predetermined magnitude. The power converter advantageously operates in only a constant-power mode regardless of loop impedance.

Floating battery feed circuit

Control circuitry used with the combination of a control switch (typically a gated diode switch GDS) which is coupled to a control (gate) terminal of a like load switch which consists essentially of first and second p-n-p transistors. The collector of the first p-n-p transistor is coupled to an anode of the control switch. The emitter of the first p-n-p transistor is coupled to the base of the second p-n-p transistor and to a control circuitry input terminal. The collector of the second p-n-p transistor is coupled to a gate terminal of the control switch. The control circuitry limits undesirable current flow into the load switch and has fewer components than commonly used control circuitry which performs a like function.

Control circuitry for high voltage solid-state switches

A protection circuit for communication equipment connected to a two conductor communication line includes a bridge rectifier having alternating current terminals connected to the conductors and to ground. The direct current terminals of the rectifier are connected to a device responsive to a range of predetermined voltage and current conditions in the conductors for reflecting foreign electrical energy.

Protection circuit

To switch a first gated diode switch (GDS1) to the 'OFF' state requires a voltage applied to the gate which is more positive than that of the anode or cathode and a sourcing of current into the gate of substantially the same order of magnitude as flows between the anode and cathode of the first switch. Control circuitry, which uses a second gated diode switch (GDSC) coupled by the cathode to the gate of the first switch (GDS1), is used to control the state of the first switch (GDS1). The control circuitry comprises a first branch circuit coupled to the gate of GDSC and to a first potential source +V1, a second branch circuit coupled to the anode of GDSC and to a second potential source +V2, and a third branch circuit coupled to the anode of GDSC and to a third potential source +V3. The first branch circuit is connected to the gate of the second switch (GDSC) and controls the state thereof. The second branch circuit maintains the state of the load switch (GDS1) and is adapted to supply up to a preselected maximum amount of current into the anode of GDSC and then to automatically reduce the amount of supplied current substantially. The third branch circuit is used to provide a surge of current during a current break operation to turn GDS1 to an OFF state.

A high voltage solid-state switch uses a dielectrically isolated lightly doped p- type semiconductor body with a heavily doped p+ type anode region, a heavily doped n+ type gate region, a moderately doped p type shield region, and a heavily doped n+ type cathode region. The shield region surrounds the cathode region. Separate electrodes contact the anode, gate, shield, and cathode regions. The gate and cathode regions also act as the collector-emitter output circuitry of an n-p-n transistor with the shield region acting as the base. With the shield (base) region forward-biased with respect to the cathode or gate regions, the n-p-n transistor is biased on and the collector and emitter are rapidly pulled close to each other in potential. With proper operating potentials applied to the anode and cathode regions, the switch rapidly assumes an 'ON' state when the potential of the shield (base) region is set to a level which biases the n-p-n transistor ON. The integral n-p-n transistor serves to rapidly turn the switch to the ON state and only marginally increases the amount of silicon area needed to implement the switch.

Integral turn-on high voltage switch

To switch a first gated diode switch (GDS) to the 'OFF' state requires a voltage applied to the gate which is more positive than that of the anode or cathode and the sourcing of current into the gate which is of the same order of magnitude as flows between the anode and cathode. Control circuitry, which uses a second GDS coupled by the cathode to the gate of the first GDS, is used to control the state of the first GDS. The state of the second GDS is controlled by a branch circuit having a relatively modest current handling capability. An n-p-n junction transistor has the emitter and collector coupled to the cathode and gate, respectively, of the first GDS, and has the base coupled through a p-n-p transistor to the input terminal of the control circuitry. The n-p-n transistor facilitates a quick turn-on of the first GDS by rapidly bringing the potentials of the gate and cathode of the first GDS to levels which are close together.

Control circuitry using a pull-down transistor for high voltage field

A miniature electronic bridge lifter for bridged telephone lines which can be mounted directly on the protector unit in the central office includes an impedance inserted serially in each side of the loop for isolating the nonactive loops from the central office termination and for switching to a low impedance connection whenever a party on one of the bridged line connections goes off-hook. A combination semiconductive and resistive voltage divider detects the voltage across the loop. The resistive component is essentially the only cross-coupling between the telephone lines. When the line voltage falls below a preselected threshold, indicating that the connected party has gone off-hook, a switch is operated to bypass the series impedances and establish a low-loss path to the common line.

Miniature bridge lifter for telephone lines

A telephone ringer isolator for isolating ringers and extending ringing range on a multiparty telephone line or for range extension only on single party lines is disclosed. The circuit includes a detector circuit for detecting the direct current superimposed on an alternating current ringing signal. A pair of biasing circuits for transistors are enabled by a properly poled ringing signal appearing between tip and ring conductors. When the transistors are enabled, a capacitor is charged to trigger a silicon-controlled rectifier. When thus fired, the silicon-controlled rectifier enables a diode bridge gate to connect the ringer between one side of the telephone circuit and ground potential. Isolation between the input and output terminals is provided by the high collector resistance of the gating transistors.

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Winfield, IL, United States of America

William F MacPherson