Abstract: A rotary compressor has a compression mechanism including main and sub bearings closing the ends of a cylinder bore and supporting a crankshaft having an eccentric portion on which a rolling piston positioned in the cylinder bore is rotatably mounted. Oil grooves are formed in the shaft holes of the bearings to receive lubrication oil from spaces defined by the rolling piston, the crankshaft eccentric portion and the main and sub bearings. The eccentric portion and the sub bearing are sized and shaped such that the oil groove in the sub bearing is always prevented from opening to the space adjacent thereto. The drawing force generated in the oil groove in the sub bearing by the rotation of a balancer attached to the lower end of the crankshaft is thereby prevented from acting on the space, thereby avoiding cavitation abrasion of the members facing the spaces.

Abstract: A conference system, in which a buffer memory is connected to the input-output of each highway for storing all its channel data for each frame. The stored data is time-divided so that a time-length obtained by dividing one frame length by an appropriate number (for example, eight) may be the operation time length of each trunk, thereby implementing real-time processing a number of trunks. Conference circuits capable of inhibiting an output for each channel are connected in parallel to the highways. During an ordinary two-party communication operation an output on the corresponding channel of the conference circuit is inhibited, and during a conference operation an output on the corresponding channel of the highway switching circuit is inhibited, by which channels allocated to telephone sets or CO lines are used for the conference without the necessity of providing channels specifically therefor.

Abstract: A control signal transmission system for a key telephone system, in which control signal information is transmitted in a parallel signal configuration between a plurality of key telephone sets and a key service unit by the use of transmission lines one-to-one corresponding to the individual key telephone sets, and in which the information between the key telephone sets is transmitted using a serial signal format of a frame configuration so that time slots of respective frames are synchronized with respect to all of the transmission lines.

Abstract: A synchronization system for a key telephone system, in which key information or the like information signal between a key service unit and each key telephone set is transmitted in the form of a time-division pulse signal under the control of a counter provided in the key service unit. The information signal has a format which is divided into a first signal from the key service unit to each key telephone set and a second signal from each key telephone set to the key service unit so as to make distinction between the first and second signals in terms of time. The first signal is disposed in a time slot preceding the second signal to provide a pair of signal groups. A one-pulse start signal is disposed in the foremost time slot of the signal groups and a one-pulse answer signal is disposed in a time slot between the first signal and the second signal.

Abstract: A key telephone system adapted to selectively connect a plurality of key telephone sets to a plurality of CO lines through a key service unit and pluralities of talking lines and control lines and provided with a calling device in at least one of the key telephone sets, in which automatic holding of the CO line is enabled upon depression of a calling key. In case of transferring the incoming call from a receiving key telephone set to a called one of the other key telephone set, depression of the individual calling switch automatically starts calling of the called key telephone set and enables the called party to recognize the incoming call by means of lamp indication and answer the calling CO line. The number of cable conductors interconnecting the key service unit and the key telephone sets is effectively reduced.

Abstract: An intercom calling apparatus in a key telephone system including a page switch for switching the transmitter from a talking circuit network to an intercom calling path while a contemporaneous call on a central office line is held by the series combination of a resister and a varistor forming a parallel circuit with the transmitter in the talking circuit network.

Abstract: An indicator comprises first means adapted for emitting a ray of light; and second means having an indicating surface for receiving the ray of light to permit the ray of light to illuminate the indicating surface. The first and second means are movable relative to each other to vary intensity of illumination of the indicating surface.

Abstract: A rotary dial device for a telephone set, in which an additional function of preventing a toll dialling is provided. In accordance with this invention, a contact is further attached to an usual dial to classify dial impulses so that when a number "1," one of numbers "2" to "9," and a number "0" are dialled, one, two and three pulses are produced respectively. The dialling function subsequent to the first dialling number "0" and the first and second dialling numbers "10" is effectively stopped by counting the classified pulses.

Abstract: A visual indicator control circuit for use in key telephone systems is disclosed. The circuit includes a plurality of light emitting diodes connected in series and operated by a plurality of transistors having collector-emitter paths connected in parallel with the light emitting diodes. Circuits are provided for controlling the respective base electrode voltages of the transistors corresponding to the use status of each line to control the light emitting diodes corresponding to the on or off states of the transistors.