Abstract:
A method to dynamically connect an originating computer to a receiving computer on a dial-up network, such as the Internet. The originating computer calls the receiving computer over the Public Service Telephone Network (PSTN); the receiving computer detects the call but does not answer it so that no PSTN charges are incurred; then both the receiving computer and originating computer call up the dial-up network and one of the computers obtains the network address of the other computer to establish a communication link between them.

Description:
FIELD OF THE INVENTION 
     The present invention relates to computer data transmission and more particularly to the transmission of setup data over the Public Switched Telephone Network (PSTN) between geographically distant computers. 
     BACKGROUND OF THE INVENTION 
     The need to exchange data between computers has never been greater. For example, new demands on traditional Point-of-Sale applications require immediate (near real time) sales data to be transmitted from retail stores to their central office. Electronic Data Interchange (EDI)&#39;s goal of paperless electronic commerce between customers and suppliers requires that computers be able to exchange order and payment information 24 hours a day. And multinational corporations with offices around the world need to be able to exchange files, send faxes, and conduct voice and multimedia sessions with employees at any time of day for minimal cost. 
     Existing methods for exchanging data (including fax and voice) between two geographically distant computers or fax machines utilize (1) dial-up point-to-point connections over the Public Switched Telephone Network (PSTN); (2) dedicated transmission connections (also known as private lines or leased lines); and (3) dial-up data network connections, like the Internet. Method 1 requires one computer to initiate a data exchange with the other by using the PSTN to establish a long distance phone call during which the two computers exchange data. This Method 1 is cost effective for weekly or monthly exchanges of small amounts of data. However, it is undesirable for lengthy data transfers, due to the toll time charges associated with long-distance phone calls. 
     Method 2 utilizes dedicated transmission lines between two computers for exchanging data. For frequent exchanges of large amounts of data, Method 2 is more cost effective than Method 1 but typically requires a fixed monthly payment for the dedicated transmission line, regardless of the amount of data exchanged. As with Method 1, the computers are able to exchange data at any time, although dedicated transmission lines do not incur the overhead or delay associated with Method 1. 
     Method 3, using dial-up data networks, like the Internet, to transfer data, improves upon Methods 1 and 2 since there are (typically) no long-distance fees associated with connecting to the Internet. Another benefit is that Internet Service Providers (ISP) provide access to the Internet at rates significantly lower than the rates for dedicated transmission lines. 
     For two computers to exchange data over the Internet at any time, they must be connected to the Internet 24 hours a day or connected at predetermined times, or use a person at one computer to place a telephone call to a person at the other computer to tell him/her to become connected with the Internet. Unfortunately, when the data transferred is infrequent and/or small in size, the cost of 24-hour connection to the Internet can be greater than the costs associated with a direct point-to-point connection over the PSTN between the two computers. And connecting at predetermined times precludes the transmission of real-time or near real-time data and does not provide any flexibility, for example, if heavy data traffic slows the communication. 
     A more cost effective method would combine the best features of Methods 1 and 3 to allow data transfers over the Internet, but not require that both computers maintain a 24-hour connection to the Internet or rely on a predetermined connection schedule. It would be ideal if there were a way that both computers would automatically, without human intervention, be able to connect to the Internet only when data exchange is required so that connect-time charges would be kept to a minimum. 
     SUMMARY OF THE INVENTION 
     The present invention seeks to minimize the costs of exchanging data over geographically separate computers and fax (facsimile) machines. It provides such cost savings by enabling two computers to use dial-up data networks (“network”), like the Internet, to exchange data and enabling them to dynamically connect to the Internet only when there is a need to transfer data by using a “callback” mechanism. At all other times, the computers are not connected to the network. 
     When one computer (the “originating” computer) determines the need to exchange data with another computer (the “receiving” computer) it uses a preconfigured mapping table to obtain the phone number associated with the receiving computer. The originating computer connects to the PSTN via a modem and dials the receiving computer&#39;s phone number, allowing the receiving computer to receive several ring pulses. The originating computer then terminates the unanswered phone call and proceeds to dial a phone number to establish a dial-up connection to the data network associated with the receiving computer. Once connected, it establishes a connection with the receiving computer. The receiving computer, by this time, has dialed up and been connected to the same data network. All of these steps are programmed in the two computers and are performed without human intervention. 
     When the receiving computer detects an incoming phone call on its modem, it extracts the Automatic calling Number Identification (ANI) information. ANI is generated by the local exchange carrier using in-band signaling to transmit information, between the ring pulses, such as the calling party&#39;s phone number and name. This is not a standard feature for phone service. A monthly fee is normally levied to allow the receiving party to obtain ANI information. Consequently, the receiving computer must arrange with its local telephone company for ANI service. 
     The receiving computer uses the originating computer&#39;s phone number, contained in the ANI information, to determine how to respond to the incoming, and as yet, unanswered phone call. If the receiving computer does not “recognize” the phone number as one from a list of originating computers&#39; phone numbers, it can answer the phone call. This allows the computer to respond appropriately to normal phone call requests to establish a point-to-point dial-up connection for data transfer or to answer an incoming fax, or to allow an individual to answer a voice call. 
     If the receiving computer recognizes the phone number (it is on the list) it does not answer the phone call. The incoming phone call is then terminated, by the originating computer, preferably after two rings. The receiving computer records, in its memory, an identification of the originating computer and the data network associated with the obtained ANI information. It dials a phone number to its Internet Service Provider to establish a dial-up connection to the data network. The receiving computer is connected with the originating computer through the data network. If the network is the Internet one computer is connected to the other using the identification of the IP address. When the computers have finished exchanging data, they disconnect. 
     This novel use of ANI, using it to synchronize two computers to become simultaneously connected to the same dial-up data network, provides a clear advantage over a 24-hour connection, since connect-time charges are accrued only when data is exchanged—once data transfer has been completed the computers disconnect from the network. Similarly, the receiving computer&#39;s use of ANI to determine when to dial-out results in reduced connect-time charges (compared to not using ANI and dialing-out with each incoming phone call). Also, ANI allows the receiving computer to connect to different data networks based on the originating computer—a system that did not use ANI would not be able to distinguish between originating computers and would always call the same data network. Finally, ANI provides the capability for non-callback-type calls to be processed conventionally, i.e., allows the establishment of a normal point-to-point dial-up connection, fax reception, or voice call (for shared phone lines). 
     In areas that do not have ANI support, and for incoming calls that do not convey ANI information (international calls, for example), another means to inform a receiving computer to connect to a particular data network is to use distinctive ring service. This service, commonly available from local phone companies, assigns a secondary phone number to an existing phone line. When a calling party initiates a phone call using the primary phone number, the ringing signals at the receiving end are normal (a single ringing tone). When the calling party initiates a phone call using the secondary number, a distinctive ring occurs (a double ringing tone). This technique is particularly useful for routing international fax calls using a fax callback device situated between the PSTN and a fax machine. When a non-distinctive ring is detected by the fax callback device, the fax call is routed directly to the fax machine, but when a distinctive ring is detected the incoming call is not answered. Instead, after the incoming call ends, the fax callback device connects to a predetermined data network in order to receive the fax transmission. Once the transmission is completed, the fax callback device disconnects from the data network. 
     In telephone calling areas that do not have ANI or distinctive ring support, an alternative means of conveying the originating computer&#39;s identity without incurring PSTN-related charges is to take advantage of a short “no-charge” window that occurs at the beginning of every phone call. This window is an anomaly of the PSTN and allows up to a one second “free” connection to be established. To take advantage of this window, as soon as the originating computer detects that the receiving computer has answered the call, it immediately terminates the connection without sending any information. When this quick hang-up is detected by the receiving computer, the receiving computer connects to a predetermined network to exchange data with the originating computer. If, when the receiving computer answers the call, the call is not immediately terminated, then the incoming phone call is handled normally. 
     The present invention in its simplest form does not require that the receiving computer use ANI, distinctive ring or the above-mentioned no-charge window. If the receiving computer is only required to connect to a single predetermined data network, and if there is no requirement for non-callback-type calls to be processed then they may be eliminated. In this case the originating computer disconnects (“hangs up”) after the first ring. The receiving computer, based on the signal of a single ring, will dial-up its predetermined network. The originating computer, after disconnecting from the PSTN after one (or two) rings, will also dial-up the same network so that the two computers can exchange data. 
     There have been suggested in the patent literature various methods for a client computer to initiate callback service from a server computer, see U.S. Pat. No. 4,876,717 and Bathrick et al U.S. Pat. No. 5,280,581. But in these patents the callback occurs only after the server computer has answered the incoming phone call and established the identity of the client computer via log-in with a password or other authentication process. Only after the authentication is established does the server computer (or another server computer) initiate a phone call to the pre-established (or just transmitted) phone number where the client computer is located. Also, in these patents, the callback is always back to the client computer and not to a dial-up network, such as the Internet. In addition, PSTN-related charges are incurred during authentication. 
     Other patents provide call forwarding capability, where the incoming phone call is forwarded to another phone number. This forwarding can occur before the incoming call has been answered or after the caller has transmitted data to the forwarding device. Finally, the telephone exchange described by Martens U.S. Pat. No. 5,329,572 provides a service that is similar to this invention but with several key differences. Martens describes how a “customer” requires a connection between two DTE (Data Terminal Equipment) devices; however, the connection request in this invention comes from one of the devices that is to participate in the connection. Also, Martens requires communication with an interoffice communication network that establishes the connection between the separate DTEs on the separate exchanges—this invention has no requirement for such an intermediary. 
     The present invention is particularly well-suited to serving (providing) on-demand data over the Internet. Such applications on the Internet are as diverse as serving data files for World Wide Web pages, providing on-demand real-time video images, transmitting faxes, providing telemetry data showing the status of a remote site at which the receiving computer is located, and two-way voice and image communication using computers as two-way voice and image transmitters and receivers. The present invention allows such data to be made immediately available to the data network by the server (originating computer) without the necessity and expensive of having the client (receiving computer) be connected to the network at any other time. 
     An advanced embodiment of the present invention enables multiple receiving computers to be employed. When one receiving computer is busy on the data network, incoming calls are redirected, using standard features of the PSTN such as busy-call-forwarding or rollover, to an alternate server (receiving computer) connected to a second phone line. This can further be extended so that while this second server is occupied, any further incoming calls can be forwarded to a third server, and so on. In this way, for example, a small company with a plurality of phone lines, each connected to a separate receiving computer, can inexpensively implement a small farm of web servers that are collectively capable of handling a high volume of requests for data files. This “farm” can either be a group of servers in the same building or alternatively may be spread over many buildings, without the need for the servers to have any communication with each other, other than their connection to the common PSTN. 
     In larger corporations, the originating computer may actually consist of several computers connected over a local area network. For example, one computer could be used to signal the receiving computer over the PSTN while a different computer might make the actual dial-up connection to the data network. The signaling computer could notify the dial-up computer over the LAN to indicate the appropriate data network to which it needs to connect. The same is true at the receiving end: the receiving computer may consist of one computer used to receive the PSTN connection request while a different computer, connected over a LAN, makes the dial-up connection to the data network. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The inventor&#39;s presently known best mode of practicing the present invention is described in the following detailed description, which should be considered in conjunction with the accompanying drawings. 
     In the drawings: 
     FIG. 1 is a block diagram which illustrates the normal, unconnected state of the originating and receiving computers; 
     FIG. 2 illustrates typical entries in the initiating computer&#39;s receiving computer contact table, a database; 
     FIG. 3 illustrates typical entries in the receiving computer&#39;s connection request table, a database; 
     FIG. 4 is a flow chart identifying the processing blocks of the initiating computer and the receiving computer and the interaction between them; 
     FIG. 5 is a block diagram which illustrates a transient PSTN connection between the originating and receiving computers used for signaling the receiving computer; 
     FIG. 6 is a block diagram which illustrates an established Internet connection by the originating and receiving computers; 
     FIG. 7 is a block diagram which illustrates the first alternative embodiment controlling communication between three, or more, computers; 
     FIG. 8 is a block diagram of the novel fax call-back device; 
     FIG. 9 is a block diagram which illustrates the normal, unconnected state of the originating and receiving fax callback devices; 
     FIG. 10 is a block diagram which illustrates a transient PSTN connection between the originating and receiving fax callback devices used for signaling the receiving callback devices; 
     FIG. 11 is a block diagram which illustrates an established Internet connection by the originating and receiving fax callback devices; and 
     FIG. 12 is a flow chart identifying the processing blocks of the fax machine and fax call-back device system of FIGS. 9-11. 
    
    
     DETAILED DESCRIPTION 
     As shown in FIG. 1, when originating computer  1  determines the need to transfer data to a receiving computer  2 , as indicated in decision block  30  (FIG.  4 ), it obtains the phone number of that computer from a table (see FIG. 2) which maps receiving computers  2  to phone numbers, as indicated in block  31 . originating computer  1  uses an attached (or integral) modem  3  to establish a connection  11  (FIG. 5) to local exchange carrier (LEC)  5  by going off-hook. It then transmits signaling tones to LEC  5  corresponding to the phone number of receiving computer  2  as indicated in block  32 . LEC  5  establishes connection  13  via a long-distance carrier  9  (LDC) to the LEC  6  located near the receiving computer  2 . 
     LEC  6  signals modem  4  attached to the receiving computer  2  of the incoming phone call  12  by generating a ringing signal and transmitting ANI information. After receiving computer  2  has had time to detect the incoming phone call  12 , as indicated in decision block  40 , and extract the ANI information, as indicated in block  41 , originating computer  1  waiting in decision block  33  terminates the phone call, as indicated in block  34 . 
     As shown in FIG. 6, originating computer  1  next uses an attached (or integral) modem  3  to establish a connection  11  to local exchange carrier (LEC)  5  by going off-hook. It then transmits signaling tones to LEC  5  corresponding to the phone number of its Internet Service Provider (ISP)  7  as indicated in block  35 . LEC  5  establishes a connection  14  to ISP  7  which then establishes connection  16  to the Internet. Originating computer  1  is now connected to Internet  10  and is ready to exchange data, as indicated in block  36 . 
     As shown in FIG. 5, when modem  4  detects an incoming phone call  12  from LEC  6 , it alerts receiving computer  2 , waiting in decision block  40 , which requests and receives the ANI information from modem  3 , as shown in block  41 . Receiving computer  2  then accesses mapping table  21 , such as the table illustrated in FIG. 3, to determine if the phone number obtained from the ANI information is contained in mapping table  21 , as indicated in decision block  42 . If the phone number is not found in table  21 , receiving computer  2  will process the phone call normally as indicated in block  43 . 
     If the phone number is found in mapping table  21 , receiving computer  2  does not answer the incoming phone call; but waits for phone call  12  to be terminated by originating computer  1  as shown in decision block  44 . As shown in FIG. 6, once call  12  has terminated, receiving computer  2  uses attached (or integral) modem  4  to establish a connection  12  to local exchange carrier (LEC)  6  by going off-hook. It then transmits signaling tones to LEC  6  corresponding to a phone number associated with the received ANI information as indicated in block  45 , and in this example, connects to receiving computer  2 &#39;s Internet Service Provider (ISP)  8 . LEC  6  establishes a connection  16  to Internet  10  via ISP  8 . Receiving computer  2  is now connected to Internet  10  and is ready to exchange data as indicated in block  47 . 
     When originating computer  1  and receiving computer  2  have completed exchanging data, originating computer  1  uses attached modem  3  to terminate the phone call to LEC  5 , as indicated in block  37 , and receiving computer  2 , in block  47 , uses attached modem  4  to terminate the phone call to LEC  6 . The originating computer returns to the state indicated by block  30  and the receiving computer returns to the state shown by block  40 , that state being illustrated in FIG.  1 . 
     In cases where a main server (the originating computer  1 ) needs to distribute data to many receiving computers  2 , it is more efficient for the originating computer to remain connected to the Internet  10  for 24-hours a day. In this case, the originating computer  1  signals the remote computer  2  and waits for the remote computer  2  to connect to Internet  10 . When the receiving computer  2  has connected, they exchange data. Once completed, the receiving computer  2  disconnects from Internet  10  while originating computer  1  does not disconnect from Internet  10 , but remains connected and begins the same process over again for a different receiving computer. 
     First Alternative Embodiment of the Invention 
     FIG. 7 illustrates an alternate embodiment in which a plurality of receiving computers are each connected to the PSTN and data network through a separate connection accessible by dialing a telephone number that is unique to each particular receiving computer. 
     When originating computer  1   a , shown in FIG. 7, determines the need to transfer data to a receiving computer  2   a,  it obtains the phone number of that computer from a table (see FIG. 2) that maps receiving computers  2   a  to phone numbers. Originating computer  1   a  uses an attached (or integral) modem  3   a  to establish a connection  11   a  to local exchange carrier  5   a  (LEC) by going off-hook. It then transmits signaling tones to LEC  5   a  corresponding to the phone number of receiving computer  2   a , as indicated in block  32 . LEC  5   a  establishes a connection  13   a  via a long distance carrier  9   a  (LDC) to the LEC  6 a located near the first receiving computer  2   a.    
     LEC  6   a  signals modem  4   a  attached to first receiving computer  2   a  of the incoming phone call  12   a  by generating a ringing signal and transmitting ANI information. After first receiving computer  2  has had time to detect the incoming phone call  12  and extract the ANI information, first originating computer  1   a  terminates the phone call. 
     Next originating computer  1   a  uses an attached (or integral) model  3   a  to establish a connection  11   a  to local exchange carrier (LEC)  5   a  by going off-hook. It then transmits signaling tones to LEC  5   a  corresponding to the phone number of its Internet Service Provider (ISP)  7   a , as indicated in block  35 . LEC  5   a  establishes a connection  14   a  to ISP  7   a  which then establishes connection  16   a  to the Internet. First originating computer  1   a  is now connected to Internet  10   a  and is ready to exchange data. 
     When modem  4   a  detects an incoming phone call  12   a  from LEC  6   a  it alerts first receiving computer  2   a  which requests and receives the ANI information from modem  8   a . Receiving computer  2   a  then accesses mapping table  21  such as the one illustrated in FIG. 3 to determine if the phone number obtained form the ANI information is contained in mapping table  21 . If the phone number is not found in table  21 , then receiving computer  2   a  processes the phone call normally. 
     If the phone number is found in mapping table  21 , then receiving computer  2   a  does not answer the incoming phone call but waits for phone call  12   a  to be terminated by originating computer  1   a . Once call  12   a  has terminated, receiving computer  2   a  uses attached (or integral) modem  4   a  to establish a connection  12   a  to local exchange carrier (LEC)  6   a  by going off-hook. It then transmits signaling tones to LEC  6   a  corresponding to phone number associated with the received ANI information as indicated in block  45  and, in this example, connects to receiving computer&#39;s  2   a  Internet Service Provider (ISP)  8   a . LEC  6   a  establishes a connection  16   a  to Internet  10   a  via ISP  8   a . Receiving computer  2   a  is now connected to Internet  10   a  and is ready to exchange data as indicated in FIG.  6 . Receiving computer  2   a  holds its connection to LEC  6   a  off-hook until it has finished exchanging data. 
     While receiving computer  2   a  is connected to Internet  10   a  a second originating computer  90  desires to establish a connection with receiving computer  2   a , it performs the same steps that the first originating computer  1   a  used. However, when the PSTN attempts to connect to the phone number where modem  4   a  resides, the PSTN system finds that this line is busy and it then dials a second number where modem  91  resides, connected to a second receiving computer  92  having duplicate data to that of first receiving computer  2   a . This dialing of said second number is a standard feature available almost universally in the PSTN. It is commonly known as busy-call-forwarding, or when used in a PBX or local system such as Centrex, it is known as rollover. In either case, the second number has been previously programmed into the PSTN so that it would automatically be called if the first number was busy. 
     Then, in a manner similar to that in which originating computer  1   a  established the network connections to exchange data with receiving computer  2   a , the second originating computer  90  establishes the network connections to exchange data with the second receiving computer  92 . When this is accomplished, receiving computer  92  and originating computer  90  are connected to the Internet and exchanging data, as a completely independent and parallel activity to that of receiving computer  2   a  and originating computer  1   a.    
     When originating computer  1   a  and receiving computer  2   a  have completed exchanging data, originating computer  1   a  uses attached modem  3   a  to terminate the phone call to LEC  5   a  and receiving computer  2   a  uses attached modem  4   a  to terminate the phone call to LEC  6   a . The originating computer returns to the state indicated by block  30  and the receiving computer returns to the state shown in block  40 , as illustrated in FIG.  1 . 
     Similarly, when second originating computer  90  and second receiving computer  92  have completed exchanging data, second originating computer  90  uses attached modem  93  to terminate the phone to LEC  5   a  and second receiving computer  92  uses attached modem  91  to terminate the phone call to LEC  6   a.    
     It can readily be seen to those skilled in the art that said forwarding means can be extended to a system having many more than two receiving computers, and in this way a very high volume of requests for service may be handled in parallel. 
     Second Alternative Embodiment of the Invention 
     When a user wants to send a fax over the Internet, he adds a special code (such as **2) to the phone number of the receiving fax machine  52 . When sending fax machine  51 , shown in FIG. 9, initiates sending the fax, the attached fax call-back device  53  detects the special code and intercepts the call, as shown in blocks  70  and  71  (FIG.  12 ). Fax call-back device  53  begins the call-back sequence by sending ringing signals to sending fax machine  51  so that it appears that the connection is proceeding normally, as indicated in block  73 . Next, fax call-back device  53  establishes a connection  61  to local exchange carrier (LEC) by going off-hook, as shown in FIG.  10 . It then transmits signaling tones received from sending fax machine  51  to LEC  55  corresponding to the phone number of receiving fax machine  52 , as indicated in block  62 . LEC  55  establishes a connection  63  via a long distance carrier  59  (LDC) to the LEC  56  located near the receiving fax machine  52 . 
     LEC  56  signals fax callback device  54  attached to receiving fax machine  52  of the incoming phone call by generating a ringing signal. Waiting in block  82 , fax call-back device  54  answers the incoming phone call  62  (block  83 ) and waits to see if incoming phone call  62  is immediately terminated as shown in block  84 . Sending fax callback device  53 , waiting in block  75 , detects that fax callback device  54  has answered incoming phone call  62  and immediately terminates phone call  61 , as shown in block  76 , to avoid any PSTN-related charges. 
     If fax call-back device  54  detects that an incoming phone call  62  from LEC  56  was not immediately terminated, fax call-back device  54  routes the incoming phone (fax) call  62  to receiving fax machine  52 , as indicated in block  85 , which receives and processes the fax normally, as indicated in block  43 . 
     If incoming phone call  62  from LEC  56  was immediately terminated, then, once call  62  has terminated, fax call-back device  54  establishes a connection  62  to local exchange carrier (LEC)  56  by going off-hook. It then transmits signaling tones to LEC  56  corresponding to a preprogrammed phone number associated with the immediately terminated call, and in this example connects to fax call-back device&#39;s  54  Internet Service Provider (ISP)  58 . LEC  56  establishes a connection  66  to Internet  60  via ISP  58 . Fax call-back device  54  is now connected to Internet  10  and is ready to receive the fax as indicated in block  87  and FIG.  11 . 
     Next attached fax call-back device  53  establishes a connection  61  to local exchange carrier (LEC)  55  by going off-hook. It then transmits signaling tones to LEC  55  corresponding to the phone number of its Internet Service Provider (ISP)  57  as indicated in block  65 . LEC  55  establishes a connection  64  to ISP  57  which then establishes connection  66  to the Internet. Sending fax machine  51  is now connected to Internet  60  and is ready to transmit the fax, as indicated in block  79  and FIG.  11 . 
     When fax call-back device  53  has finished receiving the fax from sending fax machine  51 , it terminates the connection with sending fax machine  51  as shown in block  80 , by going on-hook. After completed transmission of digitized fax data to fax call-back device  54 , fax call-back device  53  terminates the phone call  61  and  66  to Internet  60  by going on-hook, as indicated in blocks  80  and  81  and returns to the state shown by block  70  and in FIG.  9 . 
     When fax call-back device  54  has finished receiving the fax from fax call-back device  53 , fax call-back device  54  (in block  87 ), it terminates phone call  62  and  65  to the Internet  60  by going on-hook, as indicated in block  88 . After fax call-back device  54  has completed transmission of received fax to fax machine  52 , fax call-back device  54  terminates the connection by going on-hook, as indicated in blocks  89 , and returns to the state shown by block  82  and in FIG.  9 . 
     A preferred fax call-back device  100  is shown in FIG.  8 . It includes telephone line jack ports  101  and  102  (RJ-11 ports) each of which is connected to a Data Access Arrangement (DAA)  103 , 104 . A pass-thru device  105  connects the fax machine  106  to the Local Exchange Carrier (LEC)  107  in the event the call is from a non-call-back type device. The DAA  103  is connected to a 28.8 baud modem  108  and the DAA  104  is connected to a 14.4 baud fax modem  109 . The modems  108 , 109  are connected to bus  110 . Also connected to the bus  110  are the following components: CPU  11 , for example, Intel 486SX-33; Memory  112 , for example, 2 Meg bytes; and 480×240 Pixel Pen/Touch screen display  113 . The Pen Input Display, for example, operated with a plastic stick, provides a display of the numbers entered by the user. Alternatively, the device  100  may use a numerical keyboard and a display. 
     In the claims the term “computer” means a programmable digital computer or the combination of a fax machine and a call-back device. The phrase “PSTN-related charges” means charges that are incurred above and beyond normal base service charges for phone service and, in particular include per call related charges.