At+t Corp.

Edwin A Muth

Dale E Lynn

George P Cotsonas

Kenneth Kasiske

William J Casey, Iii

A public cordless telephone system includes an arrangement for informing a public handset unit when it is within the reception range of a public base unit even though all communication channels are then occupied or all public base units in the reception area are then busy communicating with other handset units. In operation, each public base unit while communicating with any public handset unit inserts in the communication channel it is then occupying spectrum energy such as is provided either by a pilot signal or a frequency shift keying (FSK) signal. By providing this additional spectrum energy along with normal voice signal energy in the communication channel, a public handset unit while searching for an available channel and interrogating this channel will be able to determine, even though the channel is occupied, that there is a public base unit within its reception range. If no available communication channel is found and a signal from one or more public base units is detected, the handset unit generates a first alerting signal for its user thereby informing the user of the one or more public base units in the area even though a telephone call may not be initiated due to all of the communication channels then being occupied. If an available communication channel is found, an attempt to establish communication with a public base unit is initiated by the handset unit over this available channel. If no response is received from a public base unit and if a signal from one or more public base units is detected, the handset unit generates a second alerting signal which thereby informs the user of the one or more public base units in the area even though a telephone call may not be initiated due to all of these public base units then being busy.

Method and apparatus for determining availability of a public base unit

A cordless telephone public base unit employed in a public telephone system in close proximity with other public base units effectively avoids contention with these other base units for access to a cordless telephone handset unit generating a service request. Contention between the public base unit and the other public base units is resolved by assigning a specific one of a plurality of times during which the base unit may respond to the service request from the handset unit. The time in which the base unit responds to the service request may advantageously be determined by a randomly generated number, the received signal strength of the service request or a combination of these two parameters. Once access to the handset unit is acquired by a base unit and communications between these two units is established on a communications channel, all other handset units and base units are prevented from interfering with the communications between these two units.

Method and apparatus for resolving contention between multiple base

In a public cordless telephone system, a cordless telephone handset unit requests and establishes a communications link with a public base unit served by a desired local service provider whenever possible. By generating a service request containing a specific carrier request code, the handset unit selectively identifies an available public base unit served by the desired local service provider and then establishes a communications link with this base unit. In response to receiving the service request from the handset unit, all public base units operated by the chosen service provider respond by providing a first acknowledgment signal. All other public base units respond by providing a second acknowledgment signal. When both such signals are received, the handset unit responds only to the first acknowledgment signal and establishes a communications link with the first base unit providing this signal. When only the second acknowledgment signal is received, the handset unit responds by establishing a communications link with the first base unit providing this second acknowledgment signal. When communications is established with a base unit providing the second acknowledgment signal, an alerting signal is generated at the handset unit thereby informing the user that even though he or she is able to make a telephone call, the desired local service provider was not reached. Collision avoidance between public base units while supporting this operation may be provided by assigning a specific one of a plurality of times during which each public base unit may respond to the service request from the handset unit.

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Red Bank, NJ, United States of America

Edwin A Muth