Telephonic communications – Substation or terminal circuitry – Conversion of signal form
Reexamination Certificate
1998-05-15
2001-02-06
Woo, Stella (Department: 2743)
Telephonic communications
Substation or terminal circuitry
Conversion of signal form
C379S355020, C379S413000
Reexamination Certificate
active
06185297
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to the field of telephony, and in particular to an improved dialer.
BACKGROUND TO THE INVENTION
Dialers are used to interface station apparatus with a line extending to the public switched telephone network (PSTN). In one application of dialers, they store access numbers of preferred carriers. Various carriers may be preferred to save cost, due to bandwidth provisions or noise specifications, due to corporate agreements, etc.
To provide the dialing function, the dialer detects an offhook condition of the station apparatus, splits the line, receives digits dialed from the station apparatus, analyzes at least some of the dialed digits, and then either adds digits to the dialed digits and redials them to the PSTN, or substitutes and redials a different set of digits.
Due to the above requirements, dialers have required an auxiliary (but typically built-in) power supply. In a corporate environment where there is a telephone room which houses a PABX, a mains source is usually close by. Personnel are usually available to program the dialer as to the alternate or auxiliary directory numbers to dial. However, in a domestic residential environment, mains power sources are not necessarily available close by the dialer. For example, it may be desirable to locate the dialer close to where a subscriber's line enters the residence, which may be beside the basement joists where there is no mains power socket.
In addition, where such a dialer is purchased from a retailer, the customer may not be sufficiently skilled to program the dialer.
In a residential environment, if the dialer would be line powered, there may not be sufficient line voltage to operate the dialer reliably, and the result would be attempted operation of the dialer in a condition which would be against regulations of the authorities. Typical residences do not have the equipment or skill set to determine whether the line voltage is sufficient to meet regulations.
A problem with telephone line powered equipment involves maintenance, i.e. how they are to be programmed and how the programs are to be updated or changed. If the unit is to be locally programmed, this requires the presence of a person who is capable of programming, which is costly to the service provider, who may have to travel to the customer premises to perform the programming.
Remote programming had been made by counting the number of calls made and then dialing a remote maintenance site after a predetermined number of calls have been made. Another method has been used by having the maintenance site dial up the site to maintain it after it answers the line.
In calling up the line powered dialer from a remote maintenance site, the audible ringing will be heard from the customer's station apparatus. If a call is made to a remote maintenance site following a certain number of calls, this can occur during a heavy traffic period on the line. Thus these methods can disturb or inconvenience the customer, which is particularly undesirable in a residence application.
Another design concern for dialers is to meet the regulatory requirements for loop voltage and current.
Another design concern for dialers is the prevention of noise outside the telephone audio band (e.g. above 3400 Hz) from reaching the telephone line, and the passage of audio signals between the subscriber side of the dialer and the telephone network side of the dialer during the interval when the dialer is outdialing digits.
Typically some type of filter has been used to prevent the out of band noise from reaching the telephone line. However, this approach tends to be limited in effectiveness because it is difficult to achieve attenuation greater than 30 to 40 dB.
A prior art approach to determine the need for an external power supply included the measurement of the voltage across the telephone line with the telephone offhook, and the use of the product in operation to determine whether it will function. This is an hit or miss situation, which can produce an unhappy customer since the customer may consider that he has purchased an inoperative product. In addition, measurement of the voltage requires the use of test equipment which may not be available in the average residence.
Sometimes a light emitting diode is used to indicate proper operation voltage. However a light emitting diode consumes electrical current which reduces the line length over which the dialer will operate.
SUMMARY OF THE INVENTION
The present invention is a subscriber line powered dialer which can automatically regulate the current/voltage characteristics of the power received from the PSTN, so as to meet regulations and thus to seize a line from the PSTN reliably.
The dialer can also confirm to a purchaser (e.g. by providing a tone in a handset of the station apparatus) either each time the station apparatus is used, or once on installation, that the line voltage received from the PSTN is satisfactory to operate the dialer. If no confirmation signal is received, the purchaser will know that an auxiliary power supply is required to power the dialer.
The line powered dialer can also automatically dial to a programming location at a predetermined time (e.g. during the middle of the night), and obtain any of operation programs, auxiliary or substitute digits to dial when certain digits are dialed on the station apparatus, and operation parameters.
In accordance with an embodiment of the invention, a telephone dialer for connection to a public switched telephone network (PSTN) and to a station apparatus, for receiving digits dialed from the station apparatus and for adding digits or substituting digits for the dialed digits and for redialing digits to the PSTN wherein the redialed digits are comprised of the dialed and added digits or comprised of substituted digits, further comprises an adjustable hold circuit for connection to the PSTN during an interval when said redialed digits are being output, for holding a line associated with the PSTN in an offhook condition, the adjustable hold circuit having a load connectable to the PSTN line which is variable with PSTN line voltage at the dialer such as to draw a variable current sufficient to meet predetermined current and voltage criteria of said line at the dialer.
In accordance with another embodiment, a telephone dialer for splitting a line between a public switched telephone network (PSTN) and a station apparatus location, is comprised of a circuit for generating subscriber line voltage and current from power supplied by the PSTN on said line and for applying said voltage and current to the line to the station apparatus location following the split, and a warning circuit for detecting voltage across a PSTN line and voltage across the line to which the station apparatus may be connected, and for providing a first signal in the event the difference in the voltages is greater than a predetermined value as an indicator that an auxiliary local power supply is not required.
In accordance with another embodiment, a telephone dialer for connection to a public switched telephone network (PSTN) and to a station apparatus, for receiving digits dialed from the station apparatus and for adding digits or substituting digits for the dialed digits and for redialing digits to the PSTN wherein the redialed digits are comprised of the dialed and added digits or comprised of substituted digits, further comprises a memory for storing data for operation of the dialer, a controller circuit connected to receive operating current from the line to the PSTN, the controller circuit drawing current which is less than a predetermined line leakage current which is less than that required to seize or hold said line, the controller for automatically controlling dialing of a predetermined directory number over a PSTN line at a predetermined time, and for receiving from a dialed location via the PSTN line and storing, said data for further operation of the telephone dialer.
In accordance with another embodiment, a telephone dialer for splitting a line between a publi
Casselman Patrick H.
Pharoah Marshall W.
Purits Valentin
Rudolph Neal
Zabel John R.
Mitel, Inc.
Pascal & Associates
Woo Stella
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