PRIVATE AUTOMATIC TELEPHONE SYSTEM WITH DIAL AND DIALLESS TELEPHONES

• US 3,809,824 A
• Filed: 03/31/1972
• Issued: 05/07/1974
• Est. Priority Date: 03/31/1972
• Status: Expired due to Term

• Current Assignee: James E. Dahlquist, Richard J. Medal
• Original Assignee: James E. Dahlquist, Richard J. Medal
• Inventors: Medal, Richard J., Dahlquist, James E.
• Primary Examiner(s): Brown, Thomas W.
• Application Number:
  US05/240,122
• Time in Patent Office: 767 Days
• Field of Search: 179/27B,39,38,37,40,84L,18BC,18BB,18BD,18BF,18E,18EA,18AB,18BG,18HB
• US Class Current: 379/48
• CPC Class Codes: H04Q 3/625 Arrangements in the private branch exchange

Abstract

A private automatic telephone system for use in schools and other locations where supervisory control over the use of the telephone system is desired, so that calls between certain telephones cannot be made without the authorization of administrative personnel. The system includes dial and dialless telephones, with the dial telephones being capable of dialing any other telephone within the system in a conventional manner, i.e., the telephone receiver is lifted and the telephone dialed to result in either a ring signal or a busy signal if the called telephone is busy. If a dialless telephone is used to initiate a call, the lifting of its receiver produces a visual indication in an annunciator light panel placed in an area having dial telephones, so that an administrator may respond by dialing the number of the dialless telephone and complete the call. The responding dial telephone may connect one or more additional telephones to the call by momentarily depressing its hook switch, thus enabling the dial telephone to receive dial tone and enable the dialing of the number of the additional telephone and establish a conference call. The administrator may either place his telephone on-hook and occasionally lift the receiver to monitor the call if desired or may permanently disconnect from the conference call by pressing a release button. The system is capable of providing two or more simultaneous independent calls depending upon the number of links that are provided to connect separate telephones in the system.

Claims

1. In a private automatic telephone system having a plurality of dial and dialless telephones, the system comprising register means for transmitting a dial tone and for receiving and transmitting a dial coding information signal responsive to the dialing of a number of another telephone at an off-hook, non-busy dial telephone, means for producing a busy signal in the event said dialed telephone is busy, means for producing a ring signal in the event the dialed telephone is not busy, call directing means adapted to be connected to any of said telephones, said call directing means being adapted to search all non-busy dial telephones and detect and connect the first existing off-hook non-busy dial telephone while isolating all other telephones from said call directing means and provide a link for connecting said off-hook dial telephone to any one of said other dial or dialless telephones when its associated number is dialed to complete a call, meaNs for initiating a call from any of the dialless telephones including an annunciator having a lighted visual display with a respective indicator for each dialless telephone, said annunciator including means responsive to the going off-hook of each dialless telephone for lighting at full brightness the respective indicator of a dialless telephone which has gone offhook, thereby enabling a person seeing a lighted indicator to respond to the associated dialless telephone by taking a dial telephone off-hook and dialing the number of said associated dialless telephone to connect said dial and dialless telephones, said annunciator further including means for maintaining at full brightness the respective indicator of each dialless telephone which has gone off-hook but has not been responded to by being called from a dial telephone, and means for maintaining at less than full brightness the respective indicator of each dialless telephone which has been responded to by being called from a dial telephone and is therefore busy.

2. A private automatic telephone system as defined in claim 1 further including sounding means associated with said annunciator to provide an audio indication of a dialless telephone going off-hook for the purpose of initiating a call.

3. A private automatic telephone system as defined in claim 1 wherein the respective indicator of each dialless telephone which has gone off-hook is maintained at full brightness until it is responded to by being called from a dial telephone, even though said dialless telephone is subsequently placed on-hook.

4. A private automatic telephone system as defined in claim 1 further including at least one link means in addition to said call directing means link, each of said link means being adapted to receive and maintain a completed call when transferred from said call directing means, thus freeing said call directing means for searching other non-busy dial telephones for a subsequent off-hook non-busy dial telephone.

5. In a private automatic telephone system having a plurality of dial and dialless telephones, call directing means having a link and being adapted to connect a first one of said dial telephones to said call directing link is response to said first dial telephone going off hook, register means for transmitting a dail tone to said first dial telephone and for receiving and transmitting a coding signal responsive to the dialing of the number of a second telephone by said first dial telephone, means responsive to said register means for connecting said telephone to said call directing link thereby establishing an initial connection between said first and second telephones, a link means in addition to said call directing link adapted to receive and maintain the connection initially made in said call directing link, transfer means responsive to completion of transmission of said coding signal for transferring the connection from said call directing link to said link means immediately upon transmission of said coding signal, means responsive to said transfer means for resetting said call directing means after transfer, thereby to free said call directing means for detecting and connecting subsequent off hook dial telephones, means associated with said link means for producing a busy signal in the event said second telephone is busy and for producing a ring signal in the event said second telephone is not busy, whereby when said second telephone is answered in response to said ring signal a talking path is established over said link means.

6. A private automatic telephone system as defined in claim 5 including two or more link means in addition to said call directing link, and link finding means for selecting an unoccupied link means into which said connection initially made in said call directing link may be transferred.

7. A private automatic telephone system as defined in claim 6 further including means for connecting an additional telephone into a connection existing in a link means to provide a Conference call among said telephones connected in said link means and said additional telephones, including means for detecting a signal initiated at a dial telephone in said original connection, means responsive to said signal for providing to said signaling dial telephone access to said call directing link while maintaining said original connection in said link means, thereby to allow said signaling telephone to dial the number of said additional telephone and causing said means responsive to said register means to establish an initial connection of said additional telephone to said call directing link, and means associated with said transfer means for transferring said additional telephone from said call directing link to said link means in which said original connection was maintained, thereby to complete the connection among said telephones in a conference call.

8. A private automatic telephone system as defined in claim 6 further including means responsive to said link finding means for temporarily maintaining said initial connection in said call directing link in the event all of said link means are occupied, means associated with said call directing link for producing a busy signal or a ring signal in the event said second telephone temporarily connected in said call directing link is busy or not busy respectively, said means responsive to said link finding means adapted to initiate transfer of said connection temporarily maintained in said call directing link to a link means when one of said link means becomes unoccupied, whereby when said second telephone is answered in response to said ring signal a talking path is established over said call directing link and maintained therein until said link finding means locates an unoccupied link means initiates transfer of the temporarily maintained connection to the unoccupied link means.

9. A private automatic telephone system for use in schools or the like where administrative control of the telephone system is desired comprising in combination, a plurality of dial and dialless telephones each having a hook switch and a ringer, a plurality of telephone lines one of which is associated with each of said telephones, call directing means including a link, said call directing means adapted to search all non-busy dial telephones and detect and connect a first off-hook non-busy dial telephone to said call directing link, register means for transmitting a dial tone to said first telephone and for receiving and transmitting a coding signal responsive to the dialing of the number of a selected second telephone by said first telephone, means responsive to said register means for connecting said second telephone to said call directing link thereby establishing an initial connection between said first and said second telephones, a link means in addition to said call directing link being adapted to receive and maintain the connection initially made in said call directing link, transfer means responsive to the completion of transmission of said coding signal for transferring the connection from said call directing link to said link means upon completion of transmission of said coding signal, means associated with said link means and responsive to said transfer means for producing a ring signal for ringing the ringer of said selected second telephone upon transfer of said initial connection to said link means, means for producing a busy signal to said first telephone in the event said second telephone is busy, and means responsive to said transfer means for resetting said call directing means subsequent to said transfer, whereby after said transfer of said initial connection said call directing means is freed to search all other non-busy dial telephones and detect and connect a subsequent off-hook dial telephone while said ringing of said second telephone ringer is accomplished while said connection is maintained in said link means.

10. A private automatic telephone system as defined in claim 9 including at least two link meanS in addition to said call directing link and link finding means for selecting an available link means into which said initial connection made in said call directing link may be transferred by said transferring means.

11. A private automatic telephone system as defined in claim 9 wherein said ring signal producing means includes a relay controlled by a flip-flop, said flip-flop normally maintained in its first stable state causing the contacts of said relay to be open and driven into its second stable state when ring signal is required causing said contacts to close, said flip-flop being set and reset to produce intermittent ring signals that are separated by pauses therebetween, thereby to produce substantially instant ringing in said second selected telephone upon completion of dialing of said selected telephone, in the event said second selected telephone is not busy.

12. A private automatic telephone system as defined in claim 11 further including means for adjusting the rate of setting and resetting of said flip-flop thereby making adjustable the duration of each of said intermittent ring signals as well as the duration of said power between said ring signals.

13. A private automatic telephone system as defined in claim 11 wherein the ring signal producing means includes a signal generator for producing an alternating current ring signal and a switching means for isolating said generator from the output of said ring signal producing means, said ring signal producing means being adapted to close said switching means to produce a ring signal in said second selected telephone when said alternating current passes through zero.

14. A private automatic telephone system as defined in claim 13 wherein said ring signal producing means includes a clock means synchronized to the frequency of said ring signal generator alternating current frequency such that said clock means is adapted to enable closing of said switching means only when said clock means signal is passing through zero.

15. A private telephone system as defined in claim 9 wherein said busy signal producing means produces said busy signal to said first telephone upon completion of dialing of said second complete telephone number in the event said second telephone is busy, the busy condition of said second telephone being detected by said ring signal producing means responsive to the absence of ring current in said second telephone indicating that said second telephone is off-hook.

16. A private automatic telephone system as defined in claim 10 including means for temporarily maintaining said initial connection between said first and second telephones in said call directing link in the event all of said link means are occupied thereby to provide a communications path in said call directing link.

17. A private automatic telephone system as defined in claim 10 wherein said first dial telephone is connected to said second selected telephone in a link means, said system further including means for sequentially connecting one or more additional telephones to provide a conference call among said first and second telephones and said one or more additional telephones, including means for detecting a signal from one of said dial telephones in said link means indicating that said additional telephone is to be added to make a conference call, means responsive to the detection of said signal for holding said first and second telephones in said link means and providing to said signaling telephone access to said call directing link thereto to allow said signaling dial telephone to receive a dial tone for dialing the preselected number of said additional telephone, said means responsive to said register means being effective to provide an initial connection of said additional telephone to said call directing link and said transfer means being effective to transfer said initial connection to said link means wherein the connection between said first and second telephone had been maintained, such that said first, seCond and additional telephones are connected in a conference call.

18. A private automatic telephone system as defined in claim 17 wherein said first dial telephone may be put on-hook without severing the connection between said first, second and additional telephones, thus permitting the person at said first telephone to take his telephone off-hook and intermittently monitor said conference call if desired.

19. A private automatic telephone system defined in claim 17 wherein said first dial telephone includes release means for permanently severing said first telephone from said conference call to enable said first telephone to initiate or receive other telephone calls.

20. A private automatic telephone system as defined in claim 10 wherein said transferring and resetting means are adapted to maintain a connection between said first and second telephones in said call directing link in the event all of said link means are occupied thereby to provide a talking path in said call directing link, and responsive to a link means becoming available, are adapted to transfer said connection between said first and second telephones from said call directing link to said available link means and thus free said call directing means for searching additional off-hook, non-busy telephones.

21. A private automatic telephone system as defined in claim 20 including means for interrupting said call directing means in the event all of said link means and said call directing means link are occupied, to permit the initiation of an emergency call.

22. A private automatic telephone system as defined in claim 10 wherein said call directing means is adapted to detect and connect a first off-hook dial telephone when said call directing means is searching in its search mode, said search mode applying voltage to all non-busy dial telephones, said call director changing from said search mode to a hold mode responsive to a non-busy dial telephone going off-hook and causing current to flow in said off-hook dial telephone which is effective to generally simultaneously remove voltage from all other previously searched non-busy dial telephones and isolate them from the call directing means.

23. A private automatic telephone system as defined in claim 22 wherein said call directing means changes from holding mode of operation to transfer mode of operation substantially upon completion of dialing of a selected telephone number associated with said second telephone, the changing of said call directing means from said hold mode to said transfer mode initiating said transferring means to transfer said connected first telephone and said selected second telephone to an available link means, which transfer initiates said resetting means to change said call directing means back into its search mode.

24. A private automatic telephone system as defined in claim 23 wherein said resetting means is adapted to automatically change said call directing means back into its search mode within a preselected time period, said time period being in excess of the time duration normally required to complete the dialing of a complete telephone number, said automatic resetting substantially reducing the possibility of a slow dialing party precluding access to the call directing means by other telephones.

25. A private automatic telephone system as defined in claim 24 wherein said resetting means automatically initiates said transferring means to transfer said connected first telephone to an available link means, said transfer initiating said busy signal producing means to produce a busy signal in said first telephone in the event dialing of said first telephone was not completed within said predetermined time period.

26. A private automatic telephone system as defined in claim 10 wherein the telephone numbers of the respective telephones are adapted to be coded to correspond to the architectural room number, of a room in which they are located.