This invention relates generally to the art of telephones, and more particularly to a cordless telephone network for enhancing public telephone systems.
As is well known, pay telephones are located at strategic places from which consumers can place calls. A difficulty with the current pay-telephone system is that one must normally be located exactly where a pay telephone is in order to place a call. Often, this is inconvenient since one must get out of his car, for example, to enter a phone booth. Similarly, in most current public telephone systems, it is necessary for telephone companies to make available separate stations, or booths, for each caller and these booths are sometimes uncomfortable and inconvenient, especially when it is raining or the booths are located in crowded or undesirable areas. Further, callers sometimes wish to spread reference papers in front of them while making calls, which is not usually possible in phone booths. Also, it is expensive for telephone companies to provide separate booths and equipment for each caller. It is an object of this invention to provide a public pay telephone system having telephones which allow a caller to remain in a chosen area, such as in his car, while making a call and which do not require telephone companies to provide separate stations for each of the callers.
A related problem to that discussed above is that it is difficult for an individual to receive a call at a public telephone booth. In this respect, a party expecting to receive a call at a public telephone must wait close by the telephone which can often be very inconvenient, especially when others are periodically using the telephone. Such situations are especially impractical for truckers who often must wait by public telephone booths at truck stops waiting for instructions from home offices, when they should be sleeping to prepare themselves for their next run. It is an object of this invention, to allow a called party to receive a call on public telephone systems while "on the go", at locations convenient to the person, such as in his car or truck or at a restaurant booth.
There are currently available cellular telephones which allow users to make and receive calls from cellular telephones located in serviced zones. In this regard, serviced zones are normally located around large metropolitan areas and these zones are divided into cells. If one owns a cellular telephone, and he is located in a serviced zone, he can place and receive calls via a cell antenna and base unit located in each cell. A problem with cellular telephone systems is that they are expensive to maintain and therefore are expensive for the users thereof. In this regard, one must currently pay a substantial monthly use fee as well as a substantial per call fee. Still further, one must pay for long distance toll charges and the cellular equipment is extremely expensive. On top of this, since it is expensive to set up a serviced cellular zone, this is not done, in rural areas. However, it is often desirable to place calls from within ones car, or otherwise "on the go", when one is in remote areas as well as when one is in metropolitan areas. Truck drivers provide a good example of those who often wish to place and receive calls from their trucks in remote areas. Thus, it is an object of this invention to provide a telephone system which allows one to place and receive calls from within motor vehicles or otherwise "on the go", which does not require the investment of relatively large sums of money in equipment, monthly fees, and per call fees for consumers and which does not require the investment of larger sums of money by telephone companies.
In recent years cordless telephones have come into use with which a party can have a base unit connected to a ground line with a transmitter and receiver for communicating with a cordless hand-held unit located up to one thousand feet (1000) away from the base unit. By using the hand-held unit, one can receive calls and place calls via the associated base station. To date, The United States Federal Communications Commission allows ten (10) channels to be used for cordless telephones, each channel having two (2) frequencies, one on which the base unit transmits and the hand-held unit receives and the other on which the hand-held unit transmits and the base unit receives. These channels are as follows:
______________________________________ TABLE OF CORDLESS TELEPHONE CHANNELS Base Hand-held transmit transmit Channel (MHz) (MHz) ______________________________________ 1 46.610 49.670 2 46.630 49.845 3 46.670 49.860 4 46.710 49.770 5 46.730 49.875 6 46.770 49.830 7 46.830 49.890 8 46.870 49.930 9 46.930 49.990 10 46.970 49.970 ______________________________________
In order to provide a certain amount of security for calls placed and received on cordless hand-held units a preset security code is normally assigned to a particular base unit and its associated hand-held unit. In this respect, the hand-held unit cannot be rung by a base unit which transmits another security code and, similarly, the base unit will not place a call for a hand-held unit which does not transmit the preset security code. In other words, the base unit and the hand unit are preset to be used one with the other to provide security.
Although current cordless telephones are quite useful in particular situations, their usefulness is unduly restricted. In this respect, one cannot use such a cordless hand-held unit unless he is near one particular base unit, and that is the base unit with which the hand-held unit is purchased or particularly preset to operate. Further, such a prior-art cordless telephone hand set does interfere with transmission of another if a mode switch thereof is moved to an active mode while the other is already having a conversation.
It is an object of this invention to provide a cordless telephone network which allows each cordless-telephone hand-held unit to be used with any of a plurality of strategically located base stations while yet providing more security than is presently available for each cordless telephone in the network.