Abstract: A cordless telephone arranged for operation in a frequency hopping system includes an arrangement which allows multiple cordless telephone portable units to operate in close reception proximity to each other and without interference while either responding to a service request from a cordless telephone base unit or in generating a service request to the base unit, also in the system. Contention between portable units in the system in responding to a service request from the telephone base is resolved through use of a polling process wherein the base unit polls each one of the portable units as part of this polling process. Each portable unit is assigned a number of acquisition channels distributed across the frequency hopping channels used for normal communications between the base unit and the portable units. These channels are different from and do not conflict with other acquisition channels respectively assigned to other portable units, also in the system.

Abstract: A cordless telephone is arranged for operation in a frequency hopping system includes an arrangement which achieves optimum utilization of multiple cordless telephone portable units by permitting these units to simultaneously access a common base unit. A physical layer of an air interface is provided by a two channel time division multiple access protocol for supporting a two channel multiple access system for the portable units. These two channels are considered as virtual channels and not dedicated to any particular telephone line, as in the case of two line telephone products. Nor are these two channels dedicated to any particular portable unit, but rather they are available for use by any portable unit in the telephone. A signaling layer of the air interface is provided for supporting the two channel multiple access system. Two types of subframes, acquisition and traffic, are illustratively provided in the air interface for the cordless telephone.

Abstract: A cordless telephone arranged for operation in a frequency hopping system includes an arrangement which achieves optimum utilization of multiple cordless telephone portable units by permitting these units to not only access a common base unit, but also to access each other. In establishing communications between portable units, a first portable unit in the system, in response to a user-initiated request at this unit, transmits a broadcast or page signal to other portable units, also in the system, using a multiple channel frequency hopping sequence. Once a second portable unit in the system responds, a communication link between the first and second portable units is established. A third portable unit in the system may also respond to the user initiated request and join the communication link existing between the first and second portable units.

Abstract: A cordless telephone arranged for operation in a frequency hopping system provides for conserving battery power in a portable unit when this unit is located remote from its charging station and in a standby state. While in the standby state, the portable unit resides in a low power monitoring mode which includes deactivating certain internal circuitry and periodically activating and deactivating other selected internal circuitry for conserving battery power. When the portable unit is periodically activated from a deactivated state, battery power is conserved through an adaptive operation that reduces considerably the length of time that the selected internal circuitry needs to remain turned on. This reduced on-time period for the selected internal circuitry is provided as long as the base unit is detected as frequency hopping with at least one other of the portable units in the system.

Abstract: Communication links are quickly and reliably established between units of a cordless telephone configured for operating in a frequency hopping system. This is achieved through specific processes which detects frequency hopping patterns that are embedded in radio frequency noise. A first process is executed by the base unit and/or each of multiple handset units in the cordless telephone for performing a link acquisition with another unit, also in the cordless telephone. In the execution of this process, multiple profile scans of the frequency hopping channels are executed to build up over time tables with information about energy in all of the channels in the frequency spectrum that are used by the units in the cordless telephone for frequency hopping. In the tables will be spectrum energy from a frequency hopping base unit or handset unit that appears as a recognizable pattern.

Abstract: A switching circuit having hybrid contactors connects the three output lines of a 3 phase AC power source to three input lines of a load, such as a motor and the like. A single pair of relay contacts is used to directly connect one output line of the AC power source to one input line of the load, whereas each of the other two phases of the AC power source are supplied to the load by one of a pair of pilot relay contacts in series with a diode-shunted one of a pair of master relay contacts. Only two extra pilot relays are used to provide a reversing function. The switching circuit further includes a zero-crossing detector, a phase-sequence detector, a control circuit including four flip-flops arranged in a tumble-down chain and a single distribution circuit having a data select circuit. The control circuit causes the making and breaking of the contacts at particular times, and in a sequence, such that arcing is prevented.

Abstract: A method and circuit for minimizing DC current offset generated by the voltage-integrating property of an inductive load. First, second and third hybrid contactors connect first, second, and third output lines of an AC power source to first, second, and third input lines of an inductive load. Each hybrid contactor includes a pair of relay contacts in parallel with a semiconductor switching unit having two antiparallel-connected silicon-controlled-rectifiers. A latching circuit and several delay circuits are used to turn on and off the hybrid contactors; the timing of the turn-on points is controlled relative to a zero-crossing of a voltage from the AC power source such that minimal DC offset current occurs.