Telephone terminal device with means for detecting abandonment of call

• US 5,521,975 A
• Filed: 08/11/1994
• Issued: 05/28/1996
• Est. Priority Date: 08/13/1993
• Status: Expired due to Fees

• Current Assignee: Hashimoto Corporation
• Original Assignee: Hashimoto Corporation
• Inventors: Hashimoto, Kazuo
• Primary Examiner(s): Hofsass, Jeffery
• Assistant Examiner(s): Wolinsky, Scott
• Application Number:
  US08/288,760
• Time in Patent Office: 656 Days
• Field of Search: 379/373, 379/70, 379/79, 379/253, 379/284, 379/252, 379/256, 379/382, 379/379, 379/377, 379/233, 379/237
• US Class Current: 379/382
• CPC Class Codes: H04M 1/654 Telephone line monitoring circuits therefor, e.g. ring detectors

Abstract

A telephone terminal device, which is activated by a predetermined number of ringing signals even if a telephone call occurred immediately after a previous caller had abandoned a call before engagement of the telephone line. When the telephone terminal device is set to standby mode, the polarity of telephone line (L1, L2) is stored in microprocessor CPU-1 via photocoupler PC-3 (or PC-4) and contact y2-1. If there is a call thereafter, ringing portion of the ringing signal is detected by photocoupler PC-3 (or PC-4) via capacitor C2. During a silent period, the polarity of the telephone line (L1, L2) is checked by the aforementioned PC-3 or PC-4 via contact y2-1 which is closed. When the polarity of the telephone line at the time of abandonment of call by a caller prior to activation of the telephone terminal device coincides with the aforementioned polarity stored, the telephone terminal device is restored to standby mode (with the counter for ranging signals being cleared).

Claims

1. In a telephone system wherein ringing signals cause a change in a polarity of a telephone line, a telephone terminal device with means for detecting abandonment of a call, said telephone terminal device comprising:

storage means for storing a value indicating polarity of a telephone line prior to reception of a ringing signal on said telephone line;

ringing signal detecting means for detecting ringing signals;

means for activating said telephone terminal device when a predetermined number of said ringing signals are counted;

means for comparing polarity stored in said storage means with polarity of said telephone line during silent portions of said ringing signals or polarity of said telephone line at time of abandonment of said ringing signals, said silent portions and said abandonment occurring prior to activation of said telephone terminal device; and

means for restoring said telephone terminal device to standby condition when said compared polarities coincide.

2. In a telephone system wherein ringing signals cause a change in a polarity of a telephone line, a telephone terminal device with means for detecting abandonment of a call, said telephone terminal device comprising:

storage means for storing a value indicating polarity of a telephone line prior to reception of a ringing signal on said telephone line;

ringing signal detecting means for detecting ringing signals;

means for activating said telephone terminal device when a predetermined number of said ringing signals are counted;

means for comparing polarity stored in said storage means with polarity of the telephone line during silent portions of said ringing signals or polarity of the telephone line at the time of abandonment of said ringing signals, said silent portions and said abandonment occurring prior to activation of said telephone terminal device; and

means capable of maintaining reception of said ringing signals when said compared polarities do not coincide.

3. In a telephone system wherein ringing signals cause a change in a polarity of a telephone line, apparatus for receiving the ringing signals from the telephone line to activate a telephone terminal device, comprising:

means for detecting a polarity of a voltage supplied by said telephone line before receiving said ringing signals,

means for checking the polarity of the voltage supplied by said telephone line after receiving at least one of said ringing signals,

means for counting said ringing signals to activate said telephone terminal device when a predetermined number of said ringing signals is received, and

means responsive to the polarity detected by said detecting and checking means for controlling said counting means to continue counting said ringing signals when the polarity detected by said checking means does not coincide with the polarity detected by said detecting means, and for resetting said counting means to an initial state when the polarity detected by said checking means coincides with the polarity detected by said detecting means.

4. The apparatus of claim 3, wherein said checking means detect the polarity during a silent period of said ringing signals.

5. The apparatus of claim 3, wherein said counting means are reset when a first sequence of said ringing signals is terminated before said telephone terminal device is activated.

6. The apparatus of claim 5, wherein said telephone terminal device is activated by said counting means when the predetermined number of said ringing signals in a second sequence is received after the first sequence of the ringing signals are terminated.

7. In a telephone system wherein ringing signals cause a change in a polarity of a telephone line, a method of receiving the ringing signals from the telephone line to activate a telephone terminal device comprising the steps of:

detecting a polarity of a voltage supplied by said telephone line before receiving said ringing signals,

checking the polarity of the voltage supplied by said telephone line after receiving at least one of said ringing signals,

counting said ringing signals in a first sequence of the ringing signals to activate said telephone terminal device when a predetermined number of said ringing signals is received,

said step of counting being carried out until the polarity detected after receiving at least one of said ringing signals coincides with the polarity detected before receiving said ringing signals, and

thereafter, counting said ringing signals in a second sequence of the ringing signals to activate said telephone terminal device when the predetermined number of said ringing signals in the second sequence of the ringing signals is received.

8. The method of claim 7, wherein said step of checking is carried out during a silent period of said ringing signals.

9. The method of claim 7, wherein said step of counting said ringing signals in the second sequence of the ringing signals is carried out when the first sequence of said ringing signals is terminated before said telephone terminal device is activated.

10. The method of claim 9, wherein said telephone terminal device is activated by the second sequence of said ringing signals when the predetermined number of said ringing signals in said second sequence is received after the first sequence of the ringing signals are terminated.