Abstract: A protective circuit for use in a subscriber's telephone circuit that includes a repertory memory and includes a battery which provides memory retention current. Circuitry permits the battery to be protected by a series current limiting resistor while maintaining sufficient voltage so that the memory maintains its integrity.

Abstract: A series regulator responds to an input voltage to produce a constant direct voltage. A resistor is connected at one end to the output of the regulator. A current carrying bus is connected between the other end of the resistor and the input of the inverter whereby current flows through the resistor producing a voltage drop thereacross and thereafter flows into the inverter to supply power thereto. An electronic switch has a closed position at which current on the bus supplied via the resistor is augmented by the current on the bus supplied via the switch. The switch has an open position at which the augmented current is not present on the bus, the switch being placed in the open position whenever a pulse appears in the control voltage and thereafter is placed in the closed position when the pulse disappears and said voltage drop is at least equal to a preselected value.

Abstract: A secretarial answering system for use with a switching system which includes a plurality of subscriber telephone stations each equipped with a buzzer, and a secretarial telephone station equipped with an audible signalling circuit and a plurality of lamp and switch pairs. A line circuit is connected to each subscriber station and monitors its busy, idle and ringing status. A processing unit periodically scans the line circuits to determine changes in the status of the subscriber stations. This processing unit then transmits subscriber station status and identification information to the secretarial telephone station. The secretarial station uses this information to provide visual and audible indications of subscriber station status. In response to operation of the switch associated with a called subscriber station, a directed call pick up or a call transfer message is transmitted by the secretarial station to the switching system.

Abstract: A secretarial telephone station for use with a secretarial answering system and a switching system which includes a plurality of subscriber telephone stations each equipped with a buzzer. The secretarial answering system is connected to the subscriber stations and transmits subscriber station busy, idle and ringing status and line identification information to the secretarial station. The secretarial station includes a lamp and switch pair for each subscriber station, a processing unit and an audible signalling circuit. The processing unit receives this information and causes the lamp associated with each of the subscriber stations to display dark, lit or flashing signals corresponding to the idle, busy and ringing status. The processing unit also causes the audible signalling circuit to provide a ringing tone wherever a lamp is flashed.

Abstract: A protective circuit consisting of two diodes which functions along with other external circuit elements to provide protection against transients for an integrated circuit utilized to generate dial pulses in an electronic telephone circuit. By means of included diodes, excessive transients are prevented from entering the integrated circuit internal circuitry and disturbing the memory included therein or other operational characteristics.

Abstract: A circuit which unlocks the signaling circuit of a feature telephone station after it has been locked. A microprocessor disconnects a tone generator from an associated keypad upon detection of operation of a lock button. The microprocessor subsequently connects the tone generator to the keypad upon detection of operation of the lock button and a predetermined master unlock code provided via the keypad. The microprocessor also connects the tone generator to the keypad upon detection of operation of the lock button followed by simultaneous operation of a predetermined plurality of telephone feature buttons.

Abstract: A hold circuit for use with a single line telephone which may or may not be equipped with extension instruments. The circuitry in response to the momentary operation of a manual switch actuates a siliconcontrolled rectifier to place a resistive load across the telephone line thus allowing the subscriber at the basic telephone instrument to go "on hook". Subsequent removal of the basic instrument handset from the hookswitch or an extension phone going "OFF HOOK" will cause the resistive load to be removed. Also included is a hold release circuit which automatically disconnects the hold circuit after a predetermined period of time.

Abstract: A current regulated pulse dialer circuit including a memory for storing predetermined sequences of telephone numbers, for use in a loop powered pulse dialing telephone. A first current source is connected to an electronic pulse dialer to provide a high impedance across the telephone line during transmission and interpulse pause conditions and a second current source is connected to an electronic pulse dialer to maintain the integrity of information stored in the memory portion of the dialer circuitry.

Abstract: An amplifier combining the properties of high gain, wide band audio response with input signal conditioning, constant current output for use on two wire systems and compound negative feedback for resistance to oscillation in acoustic feedback environments. The direct coupled amplifier combines a modified cascode stage with a composite connected transistor output stage. It is intended primarily for use in two wire communication of voice transmission such as in telephone handsets or telephone instruments.

Abstract: A dual timing circuit for use with a subscriber's telephone circuit operated in response to two manual switch operations to simulate the placement of the subscriber's phone in the "on-hook" condition for two different predetermined periods of time. One "on-hook" period being for the operation of transfer circuitry in an associated PABX and the other period being for the initiation of a new call.

Abstract: An amplifier for use with an electret microphone utilized as a telephone transmitter in a hand held telephone unit or handset. Incorporated into the circuitry is a band pass filter which substantially inhibits feedback "singing" which occurs because of reflection when the handset or telephone unit is placed in a downward position on a hard surface or similar environment. The filter circuitry employs the source resistance of the telephone transmitter and the input resistance of a transistor amplifier stage as elements of the included filter circuitry.

Abstract: A telecommunication network has a plurality of tandem node switches interconnected by trunks. Each switch generates message detail records (MDR) which are transmitted by data links to a network control center. In response to complaints, an NCC operator can start a mechanized search of MDR to retrace the path a call had earlier taken. The retraced path may be graphically illustrated on a display network map. Data from each call trace may be stored in a call trace log for subsequent retrieval.

Abstract: A telecommunication network includes a number of switches interconnected by groups of trunk circuits. Trunk traffic data is generated by the switches and transmitted to a network control center where it is stored in a traffic database. The network control center includes a system for mechanically generating periodic traffic reports and performing calculations leading to recommendations pertaining to additions or deletions of the number of trunks in a group necessary to maintain an optimum size network.

Abstract: A telecommunication network has a plurality of tandem node switches interconnected by trunk circuits. A network control center controller mechanically administers internodal conference calls by storing data pertaining to a scheduled conference call. Prior to the scheduled time, the data is downloaded to the tandem node switches which set an internodal conference bridge. Participants in a conference call first dial a bridge access number and then a password which assures security.