Method and apparatus for determining when a telephone handset is off-hook

• US 4,958,371 A
• Filed: 04/19/1988
• Issued: 09/18/1990
• Est. Priority Date: 04/19/1988
• Status: Expired due to Fees

• Current Assignee: Control Data Corporation (Ceridian HCM Holding, Inc.)
• Original Assignee: Control Data Corporation (Ceridian HCM Holding, Inc.)
• Inventors: Fourdraine, John D., Kern, Matthew F., Welsh, Russell J., Damoci, Joseph A.
• Primary Examiner(s): Ng, Jin F.
• Assistant Examiner(s): Chan, Wing F.
• Application Number:
  US07/183,065
• Time in Patent Office: 882 Days
• Field of Search: 379/106, 379/107, 379/98, 379/377, 379/96, 379/97, 379/385
• US Class Current: 379/377
• CPC Class Codes: H04M 11/06 Simultaneous speech and data transmission, e.g. telegraphic transmission over the same conductors

Abstract

Apparatus in an automatic telecommunications system which communicates between a central location and at least one remote location over the switched telephone network, senses changes in loading of the telephone line which correspond to a telephone going off-hook, to serve as an indication that a telephone has gone off-hook and to cause the automatic telecommunications system to relinquish its use of the telephone line, or not to go off-hook if a telephone is in use.

Claims

1. In an automatic telecommunication system including a central location and at least one remote location and wherein a data reporting system including a modem is situated at the remote location for establishing data communications with the central location over the switched telephone network, the improvement comprising means for determining prior to initiating communications with the central location whether a telephone at the remote location is off-hook and for inhibiting communications with the central location if a telephone is off-hook, and further comprising means for determining during the time that communications are established with the central location whether a telephone at the remote location goes off-hook comprises means for generating a test signal and applying the test signal between ring and tip of a telephone line, first and second integrator means having respectively short and relatively long integration time constants for integrating the test signal, comparison means for comparing the integrated signal outputs of said first and second integrators, whereby a substantial difference between the integrated signal outputs of said first and second integrators is indicative that an additional load has been placed between tip and ring of the telephone line, corresponding to a telephone going off-hook.

5. Apparatus in accordance with claim 1 or 3, wherein said test signal is a predetermined low frequency signal and different from the frequency of the modem signal in frequency.

2. In an automatic telecommunication system including a central location and at least one remote location and wherein a data reporting system including a modem is situated at the remote location for establishing data communications with the central location over the switched telephone network, the improvement comprising means for determining prior to initiating communications with the central location whether a telephone at the remote location is off-hook and for inhibiting communications with the central location if a telephone is off-hook, and further comprising means for determining during the time that communications are establishing with the central location whether a telephone at the remote location goes off-hook comprises first and second integrator means having respectively short and relatively long integration time constants for integrating the data communications signal being transmitted by the modem to the central location, comparison means for comparing the integrated signal outputs of said first and second integrators, whereby a substantial difference between the integrated signal outputs of said first and second integrators is indicative that an additional load has been placed between tip and ring of the telephone line, corresponding to a telephone going off-hook.

3. A method of operating an automatic telecommunication system including a central location and at least one remote location and wherein a data reporting system including a modem is situated at the remote location for establishing data communications with the central location over the switched telephone network, comprising the steps of determining prior to initiating communication with the central location whether a telephone at the remote location is off-hook and inhibiting communications with the central location is a telephone is off-hook, and further comprising the step of determining during the time that communications are established with the central location whether a telephone at the remote location goes off-hook includes generating a test signal and applying the test signal between ring and tip of a telephone line, providing the first and second integrator means having respectively short and relatively long integration time constants for integrating the test signal, comparing the integrated signal outputs of said first and second integrators, whereby a substantial difference between the integrated signal outputs of said first and second integrators is indicative that an additional load has been placed between tip and ring of the telephone line, corresponding to a telephone going off hook.

4. A method of operating an automatic telecommunication system including a central location and at least one remote location and wherein a data reporting system including a modem is situated at the remote location for establishing data communications with the central location over the switched telephone network, comprising the steps of determining prior to initiating communication with the central location whether a telephone at the remote location is off-hook and inhibiting communications with the central location if a telephone is off-hook, and further comprising the step of determining during the time that communications re established with the central location whether a telephone at the remote location goes off-hook includes providing first and second integrator means having respectively short and relatively long integration time constants for integrating the data communications signal being transmitted by the modem to the central location, and comparing the integrated signal outputs of said first and second integrators, whereby a substantial difference between the integrated signal outputs of said first and second integrators is indicative that an additional load has been placed between tip and ring of the telephone line, corresponding to a telephone going off-hook.