Various forms of monitoring and reporting systems are often associated with vending machines. Such systems can provide periodic monitoring and reporting of various events within the machines, such as inventory changes, maintenance requirements, service calls, cash receipts, demand for specific products, sold-out and alarm conditions, among others.

Some monitoring and reporting systems include a central computer complex which receives data from multiple vending machines at remote locations. In such systems, a communication link is established between the central computer and the individual machines through the use, for example, of standard telephone lines or radio communications. At predetermined intervals, each vending machine accesses the communication link and calls the central computer.

Alternatively, the central computer can access the vending machines at specified times. Once communication. is established, the vending machine can transmit pertinent information about its status. Such systems can help eliminate unnecessary service calls and facilitate better supply route planning. The monitoring and reporting systems can lead to improved auditing practices as well as increased sales.

When telephone lines are used to establish communications between the central computer and an individual vending machine, the lines can be either dedicated or non- dedicated. Using non-dedicated lines can reduce the operating costs of the system and eliminate the additional installation costs associated with dedicated lines. While the use of non- dedicated lines provides certain advantages, such

communications increase the likelihood of unauthorized access to data and information stored in the vending machine and increase the possibility of tampering with software programs or other data stored in the vending machine.

SUMMARY In general, according to one aspect, a method of establishing communications between a vending machine audit module and a central station includes receiving an incoming communications call intended for the vending machine audit module. A determination is made by the audit module as to whether the incoming call was initiated by a central station associated with the vending machine. The call is answered only if it is determined that the incoming call was initiated by the central station.

One or more of the following features may be present in some implementations. Determining whether the incoming call was initiated by the central station can include using a caller identification function. For example, a series of tones and/or a ringing signal associated with the incoming call can be monitored. Furthermore, determining whether the incoming call was initiated by the central station can occur prior to establishing an off-hook condition.

Vending machine information may be sent from the audit module to the central station after answering the call. In addition, a signal indicative of the loop saturation signal on the telephone line can be monitored, and the call can be terminated automatically if the monitoring indicates that another device or party is using the telephone line.

According to another aspect, a method of establishing communications between a vending machine audit module and a central station includes determining whether there is activity on a telephone line coupled to the audit module. A telephone call is initiated by the audit module to the central station

via the telephone line only if it is determined that the telephone line is not in use.

Various implementations may include one or more of the following features. Determining whether there is activity on the telephone line can occur prior to establishing an off-hook condition. Additionally, determining whether there is activity on the line can include monitoring audio signals on the telephone line and/or monitoring a signal indicative of a loop saturation signal on the telephone line.

After initiating the call, a check can be made to determine whether an outbound ringing signal occurs. The call can be terminated automatically if the central station does not answer the within a specified period of time. After the call is answered, vending machine information can be sent from the audit module to the central station.

In another aspect, an audit module is configured to monitor vending machine events when coupled to a vending machine. The audit module can transfer monitored vending machine information to a central station via a telephone line.

An interface circuit is connected to the audit module and can be connected to the telephone line. The interface circuit includes circuitry that can be activated by the audit module to sense caller identification signals on the telephone line without causing an off-hook condition and to provide the caller identification signals to the audit module. The audit module is further configured to answer a call on the telephone line only if the audit module determines that the caller identification signals indicate that the call was initiated by the central station.

One or more of the following features may be present in some implementations. The interface circuit can include circuitry that senses a ringing signal associated with an incoming call on the telephone line and provides to the audit module a signal indicative of the presence of the ringing signal. The audit module can be configured to activate the circuitry that senses the caller identification signals in response to receipt of the signal indicative of the presence

of the ringing signal. The caller identification signals can include, for example, a series of tones and/or a ringing signal.

Furthermore, the interface circuitry can provide a signal indicative of a loop saturation signal to the audit module. The audit module can be configured to terminate the call if the signal indicative of the loop saturation signal indicates that another party or device is using the line.

The interface circuit also can include circuitry that can be activated by the audit module to sense whether the telephone line is in use without causing an off-hook condition and to provide one or more signals to the audit module indicative of whether the telephone is in use. The audit module can be configured to establish an off-hook condition and initiate a call to the central station via the telephone line only if the audit module determines that the telephone line is not in use.

Various implementations may include one or more of the following advantages. Use of a caller identification function allows the audit module to determine that the call was initiated by the central station prior to answering the call.

The likelihood of unauthorized access to information stored in the audit module can, therefore, be reduced. The invention is particularly useful in situations where a non-dedicated telephone line is used for communicating vending machine information to the central station. Various features allow the audit module to give priority to other parties or devices which may be using or attempting to use the telephone line.

Other features and advantages will be readily apparent from the following description, the drawings, and the claims.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram of an exemplary vending machine audit system according to the invention.

FIGS. 2 and 3 are flow charts of methods according to the invention.

FIG. 4 is a schematic diagram of a call identification interface circuit according to the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS As shown in FIG. 1, an interface circuit 18 provides a caller identification (caller ID) function in connection with an audit module 10 in a vending machine 12. As used in the following description, the term''vending machine"includes, but is not limited to, machines for vending beverages, snacks, candies, toiletries, toys or other items, as well as machines for providing services, such as an ATM machine or a kiosk.

Preferably, a non-dedicated telephone line 14 is used for communications between the vending machine 12 and a central station 16. For example, a standard PSTN line can be used as the communications line 14 to allow the vending machine 12 to share an existing telephone line or extension with other devices such as a facsimile machine 20 or personal computer 22.

In general, the audit module 10 can be configured to monitor various signals or other events in connection with the vending machine 12. For example, some of the monitored signals may provide an indication of the status of product inventory or the amount of currency in the vending machine.

Some signals may indicate alarms or other conditions in the vending machine. Information regarding the monitored events can be stored by the audit module 10. Periodically, the central station 16 can request and receive status reports from the audit module 10 over the telephone line 14. Information stored by the audit module 10 can be transferred to the central station 16 for further processing. The audit module 10 also can initiate calls to transfer previously monitored vending machine information to the central station 16.

When the central station 16 initiates a call to the audit module 10 (FIG. 2, step 100), the presence of a ringing signal associated with the incoming call is sensed by the audit module (step 102) and a series of tones is provided over the telephone line 14 to identify the calling party. In some cases, the ring itself is distinctive. The series of tones, the distinctive ring or both can represent the caller ID. By providing the caller ID function at the vending machine end of the communication link, a determination can be made as to whether the source of an incoming call is the central station 16 or some other party or device. The caller ID function allows the audit module to listen to the tones and/or the ringing signal (step 104) and determine whether to answer the call by completing the connection. In particular, the audit module 10 determines whether the tones and/or ringing signal match an identification of the central station 16 stored by the audit module (step 106). If the audit module determines that the party initiating the call is a party or device other than the central station 16, the call is not answered (step 108), thereby preventing the vending machine 12 from intercepting calls intended, for example, for another device 20,22 connected to the telephone line. If the caller ID function indicates that the central station 16 is initiating the call, then the call is completed by opening a communication channel (step 110). Once the channel is established, the audit module 10 and central station 16 can perform a"handshaking"routine and the audit module can send previously monitored vending machine information to the central station (step 112). Incorporating the caller ID function into the vending machine audit module 10 can help reduce the security risks associated with the use of the non- dedicated line 14.

When the audit module 10 needs to initiate a call to the central station 16, a control signal is applied to the caller ID interface circuit 18 to allow monitoring of the tone signals present on the line 14 without drawing sufficient current to trip the controls at the central station 16 and

generate an off-hook condition. Prior to causing an off-hook condition and dialing out, the audit module 10 preferably checks or"snoops''whether there is currently any activity on the telephone line 14 (FIG. 3, step 120). If the telephone line 14 is currently in use, then the audit module 10 reschedules the call and disables its monitoring of the telephone line activity (step 122). On the other hand, if the line 14 is not is use, the audit module 10 checks for a dial tone (step 124). If a dial tone is not present, the audit module 10 hangs up (step 126) and can retry to establish a call at a later time. Assuming the dial tone is present, the audit module 10 dials the telephone number associated with the central station 16 (step 128). The audit module 10 listens for an outbound ringing signal to confirm that an attempt is being made to call the central station 16 (step 130). Once the central station 16 answers the call (step 132), a handshaking routine can be performed and the audit module 10 can send previously monitored vending machine information to the central station 16 (step 134).

Details of an exemplary caller identification interface circuit 18 are illustrated in FIG. 4. A tip and ring lead pair (not shown) that form the telephone line 14 can be connected to corresponding leads 14A, 14B in the interface circuit 18. The interface circuit 18 also has multiple leads for connection to the audit module 10 as shown in FIG. 4.

The interface circuit 18 includes surge protection circuitry 30 to prevent damage to the interface circuit as a result of electrical surges. In some implementations, the surge protection circuitry 30 includes a metal oxide varister.

Ring detection circuitry 32 can sense ringing signals appearing on the line 14. The circuit 18 also has snoop circuitry 34 that can be switched between high and low impedance states. When switched to the low impedance state, an"off-hook''condition is established. When switched to the high impedance state, the snoop circuitry 34 prevents a load from being presented to the tip/ring pair and allows the audit module 10 to monitor the status of the telephone line 14

without establishing an off-hook condition. The snoop circuitry also allows the audit module 10 to monitor the telephone line 14 to determine whether the line already is being used by another device, such as the facsimile machine 20 or the personal computer 22.

A bridge circuit 36 provides power to the telephone line side of the of a hybrid converter 38. The hybrid converter 38 is a 2-to-4 wire converter which balances the line 14 between the tip and ring leads 14A, 14B and separates the incoming and outgoing audio signals from one another.

Incoming signals on the line 14 can be passed to a first linear coupler 42 that, in the illustrated implementation, includes a pair of optical transmitters 44,46 and a dual light detector 48. One transmitter 44 is used for transmitting information regarding a ringing signal. The other transmitter 46 is used for transmitting information regarding the caller ID tones and analog (audio) signals from the telephone line 14. Signals relating to caller ID tones are provided to the audit module 10 at an input pin labeled RXOUT. Signals relating to the presence of a ringing signal are provided at an input pin labeled RNG. An indication of the loop saturation voltage on the line 14 is provided to the audit module 10 at an input pin LSAT. The loop saturation voltage can be used to determine whether another device or party is attempting to use the line 14, for example, when the audit module 10 is already using the line 14.

Outaoing signals from the audit module 10 are passed through the second linear coupler 50, which also includes two optical transmitters 52,54 and a dual light detector 56. One transmitter 52 is used for passing either of two signals from the audit module 10: a first signal (SNP) that activates the snoop circuit 34 and a second signal (OFFHK) that establishes an off-hook condition to connect the audit module 10 to the tip and ring leads 14A, 14B. When the OFFHK signal or the SNP signal is asserted by the audit module 10, a corresponding signal is passed via a demultiplexer 66. The second transmitter 54 in the coupler 50 transmits analog (audio)

signals received from the TXIN pin on the audit module 10.

Analog signals transmitted from the TXIN pin are passed to the telephone line 14 via a buffer amplifier 72 and the hybrid converter 38.

The circuit illustrated in FIG. 4 also includes multiplexers 60,62, demultiplexer 64, comparator 74, inverting amplifiers 76,78 and amplifiers 68,70. In some implementations, transformers can be used instead of the linear couplers.

The interface circuit 18 can be can be implemented, for example, using an optical data access arrangement chip, model DAA 2000, available from Siemens Components, Inc.

Operation of the caller identification interface circuit 18 is now explained with respect to incoming and outgoing calls. When the central station 16 initiates a call to the audit module 10, the ringing signal is sensed by the ring detection circuitry 32. A corresponding signal is provided to the RNG pin of the audit module 10. In response sensing to the presence of the ringing signal, the audit module 10 asserts the SNP signal to activate the snoop circuitry 34. As previously explained, activating the snoop circuitry 34 does not draw enough current to generate an of- hook condition. A series of tones identifying the source of the call are received at RXOUT and are monitored by the audit module 10. The audit module 10 may also monitor the loop saturation voltage based on a signal at the LSAT pin. The audit module 10 compares the monitored signals to information stores in a database 80 to determination whether the caller identification data associated with the incoming call matches the caller identification data for the central station 16. If the audit module 10 determines that the central station 16 is the source of the incoming call, then the audit module asserts the OFFHK signal to complete the call. Incoming analog signals, such as modem"handshaking''and central signals from the central station 16 are received at the RXOUT pin of the audit module. Outgoing analog"handshaking''vending machine data signals from the audit module 10 are transmitted from the

TXIN pin. During the call, the audit module 10 can monitor the loop saturation voltage based on the signal at the LSAT pin. In the event that the loop saturation voltage indicates that another party or device has established an off-hook condition on the line 14, the audit module 10 terminates its connection on the line. Another attempt to establish communication between the central station 16 and the audit module 10 can be make at a later time.

When the audit module 10 initiates a call, it asserts the SNP signal and monitors signals at the RXOUT and/or LSAT pins to determine whether there is any activity on the line 14, in other words, whether the line 14 already is in use.

While the snoop circuitry 34 is activated, insufficient current is drawn to generate an off-hook condition. The audit module 10 can include a digital filter, for example, to selectively detect whether audio signals within a particular frequency range are present on the line 14. If the audit module 10 determines that the line 14 is not in use, it checks for the presence of a dial tone based on signals at the RXOUT pin. If the dial tone is present, the audit module 10 asserts the OFFHK signal and dials the central station's telephone number. The audio signals for the telephone number are transmitted from the TXIN pin. The audit module 10 then monitors signals at the RNG pin to confirm that an outbound ringing signal occurs. If a busy signal is detected, then the audit module 10 terminates the call. Similarly, the audit module 10 can be programmed to terminate the call if the central office 16 does not complete the call within a specified time. Once the central station 16 completes the call, analog audio signals are received and transmitted by the audit module 10 at the RXOUT and TXIN pins, respectively. As previously noted, during the call (or during an attempt to establish the call), the audit module 10 can monitor the loop saturation voltage. If the monitored signal indicates that another party or device is using or attempting to use the line 14, the audit module 10 terminates its connection on the line.

Thus, the audit module 10 can be programmed to give priority to other users of the telephone line 14.

Other implementations are within the scope of the following claims: