Abstract: A spring tension fuse clip is disclosed having a wire wrap leg formed integrally with the spring clip. The clip is formed from a single piece of material having a gauge heavy enough to satisfy the wire wrap terminal requirement while at the same time satisfying the spring tension fuse clip requirement. This result is achieved by coining the clip only at certain bends to reduce the spring tension to the desired amount. The clip is mounted to a flat surface by a locking tab on the wire wrap leg.

Abstract: A multilink intercom is disclosed having hands free answer capability on each of the links. The circuit is arranged for use with the standard key telephone system and is station oriented such that concurrent hands free communication connections can be utilized on each of the links. A common selector is used to serve all of the links and the hands free detector and control circuitry at each station is shared among all of the intercom lines at that station.

Abstract: An electronic key telephone line circuit is disclosed for controlling the hold and disconnect conditions with respect to associated telephone stations in response to transient signals generated upon on-hook to off-hook and off-hook to on-hook transitions of those stations. Due to the nature of the switchhook contacts, the tip and ring leads open before the A-lead opens. Since the disconnect condition is determined from a transient signal caused by the tip and ring lead opening together with an A-lead open, and since by its very nature the transient response of the tip and ring lead transition can be finished before the A-lead opens, timing is used to delay the transient signal to insure that the line circuit goes into the proper mode.

Abstract: There is disclosed a circuit for generating tone signals from clocking signals present on each key telephone line circuit. The tone signals are transformer coupled onto the communication leads by an optional plug-in-board arrangement. In present installations music-on-hold is provided by connecting an external music source to each line card. There is also disclosed an arrangement for utilizing the optional plug-in-board to provide either tone-on-hold or music-on-hold by simply reversing a plug-in connector.

Abstract: There is disclosed a circuit for providing various lamp signals to a line lamp of a key telephone station. The circuit is arranged with a single ac switch or triac for each line circuit. The triac is driven at the desired rate by a circuit which generates a series of phase-shifted digital zero crossing signals having the desired duty cycle rate. Advantage is taken of the fact that the triac only requires energization at the zero crossing of the ac signal.

Abstract: A fuse clip assembly is disclosed for use with alarm type fuses. The assembly includes a forward spring tension clip, a rear spring tension clip and an alarm terminal. The rear clip is shaped to thrust the fuse forward while the forward clip is designed with a shoulder to position the fuse. The alarm terminal is positioned to catch an extended fuse alarm terminal and is shaped to securely capture the terminal to insure positive electrical contact for alarm purposes. An arrangement is disclosed which provides visual-only alarm indications.

Abstract: A handle is disclosed for use in conjunction with a key telephone printed wiring board. The handle is constructed having windows along the front surface and electrical contacts grouped behind each window. A multicontact connector is optionally connected to various of the contacts within each group and the group of contacts to which the connector is attached at any given time is easily ascertained by viewing through the associated window. The window, in addition to providing a means for determining the selected options without resorting to the removal of the board from the network, also serves to protect the individual connectors from inadvertent removal.

Abstract: In order to reduce the signal loss in a telephone line switching and conferencing system there is interposed between each line and the switching matrix a monobus port circuit arranged to convert a transmitted telephone signal into an equivalent current source. An opto-coupled hybrid replaces the port circuit transformer and serves to provide the desired voltage to current conversion. The currents from several monobus circuits are added in a bus resistor before distribution back to the individual monobus circuits as a voltage where the original signal is subtracted from the bus signal. The resultant signal is transmitted to the telephone receiver via the opto-coupled hybrid. When the switching matrix crosspoint resistance is negligible, the component of the bus voltage measured at the current source output which results from current generated from each port circuit is equal and opposite in magnitude to the voltage generated in the port circuit.

Abstract: There is disclosed an electronic key telephone line circuit having a communication path interface capable of being connected across the communication pair during both the busy and idle conditions of the line circuit. The circuit is arranged such that both the pre-ring test and the impedance test from the central switching machine are satisfied while at the same time presenting a linear impedance for communication signals. Opto isolators are used and coupled with lightning surge protection and a capacitance and resistance bridge to allow permanent connection across the communication pairs. The circuit includes a hold bridge impedance, separate from the signal detection circuitry, switchable across the communication path.

Abstract: An off-premises line circuit is disclosed which allows two telephone stations separated by a distance greater than lamp range to share a common central office or PBX line. Lamp signals as well as hold release commands are exchanged between stations by a signaling pair of leads. The off-premises line circuit is arranged so that either station may release the hold condition without regard as to which station established that condition.

Abstract: A wired logic PBX switching system is disclosed in which a camp-on circuit is used to provide automated call hold service. A station user places an existing call on hold by flashing the station switchhook contacts and dialing a predetermined code. The dialing of the code disconnects the station from the first call and places the trunk circuit serving the first call on hold. A second call may then be placed from the station. Upon termination of the second call, the hold condition is removed from the trunk circuit and a connection is reestablished from the trunk circuit to the station.

Abstract: A key telephone system is disclosed in which a direct station selection (DSS) arrangement reduces the number of operations required for the attendant to extend an incoming central office call to a station. The operation of one or more DSS keys on any of the attendant consoles in the key telephone system automatically places the calling central office line on hold and establishes a communication path through the DSS key contacts from the attendant to the selected station. DC bias on this communication path activates a loudspeaker and microphone arrangement in the selected station so the called party may converse with the attendant "hands-free." Additionally, the DSS arrangement provides the capability of utilizing any station in the key telephone system as the attendant position.

Abstract: A switching system is disclosed for interconnecting both the audio and wideband communication leads of communicating telephone stations. The system utilizes an auxiliary switching network separate from the regular audio network for handling the wideband portion of each interconnection. The connections through the auxiliary network are identified for control purposes by tracer signals applied to a called line and detected on the calling line. The tracer signals are applied and detected without interfering with the regular switching network and without major modifications to the existing network.

Abstract: A cail denial circuit is disclosed for restricting selected calls outgoing from a PBX or key telephone system. The circuit is arranged to handle both dial pulse signaling and multifrequency tone signaling from the same station while at the same time being arranged to prevent a mixture of the two types of signaling on the same call. One dial pulse detector is utilized for each line in conjunction with a multifrequency tone detector shared by all of the lines. A continuously operating scanner sequentially causes the registered digits, both from the individual dial pulse detectors and from the common tone detector, to be supplied to a common check circuit on a time-shared basis.

Abstract: A monobus conference arrangement is disclosed for use in a key telephone system. A conference circuit is serially inserted on each line and is arranged with an impedance element common to all of the stations using the line. In addition, a monobus circuit replaces the conventional hybrid in each station set. To avoid the problem of having more than one such impedance element connected in a multiline conference, the system is arranged so that current flows in a first direction through the conference circuit associated with the first-connected line and in a reverse direction through subsequently connected line conference circuits. Under control of the reverse current flow, the common impedance elements associated with the reverse current line conference circuits are removed from the connection.

Abstract: In order to reduce the signal loss in a telephone line switching and conferencing system there is interposed between each line and the switching matrix a monobus port circuit arranged to convert a transmitted telephone signal into an equivalent current source. The currents from several monobus circuits are added in a bus resistor before distribution back to the individual monobus circuit as a voltage where the original signal is subtracted from the bus signal. The resultant signal is transmitted to the telephone receiver. When the switching matrix crosspoint resistance is negligible, the component of the bus voltage measured at the current source output which results from current generated from each line is equal and opposite in magnitude to the voltage generated in the line. In any given line these voltages cancel each other, thereby eliminating the feedback signal.

Abstract: In order to reduce the signal loss in a telephone line switching and conferencing system there is interposed between each line and the switching matrix a monobus port circuit arranged to convert a transmitted telephone signal into an equivalent current source. The currents from several monobus circuits are added in a bus resistor before distribution back to the individual monobus circuit where the original signal is subtracted from the bus signal. The resultant signal is transmitted to the telephone receiver. When the switching matrix crosspoint resistance is negligible, the component of the bus voltage measured at the current source output which results from current generated from each line is equal and opposite in magnitude to the voltage generated in the line. In any given line these voltages cancel each other, thereby eliminating the feedback signal.

Abstract: A key telephone system is disclosed in which intercom calls may be answered "hands-free" at the called station. Intercom calls are originated in the standard manner, with the subscriber picking up the handset at the calling station and dialing the number of the called station. A voice communication path is established through the station selector to the telephone set represented by the dialed number. DC bias on this communication path through the station selector activates a loudspeaker and microphone arrangement in the called telephone set. The called party may thus converse "hands-free" with the calling party by utilizing the activated loudspeaker and microphone of the station set, and need not manipulate the station set for the duration of the conversation.

Abstract: A PBX switching system is described in which a queue is used to provide sequential serving of attendant directed calls. This is accomplished by sequentially storing the identity of the calling circuit for each newly arrived attendant directed call in an attendant queue. When an attendant position becomes available, the calling circuit identity stored longest in the queue is used to directly select the associated calling circuit and to connect this circuit to the attendant.

Abstract: A call denial circuit for use in a key telephone system is arranged to operate in response to a communication line reversal from the central office to create a timed interval during which the A leads from the associated key stations are observed. If any station having unrestricted capability is off-hook and active during the timed interval, the call denial circuit is inhibited and the call proceeds in the normal manner. At the expiration of the timed interval the call may continue even though only restricted stations remain on the established connection. The circuit is arranged so that a station may have some lines which are restricted and some lines which are unrestricted.