Cordless telephone instrument

Abstract: A cordless telephone instrument is improved in that, even when a portable unit is not in use, it can be determined and notified to the user whether the portable unit is inside or outside of an operational area of the portable unit. In portable unit 2, portable unit timer 28 counts a predetermined first reference time and outputs a time-out signal for each first reference time. Every time the time-out signal is outputted, a registration signal is transmitted from portable unit radio circuit 21 toward a fixed unit. When the registration signal is received by fixed unit radio section 12, fixed unit 1 transmits a response signal toward portable unit 2. Portable unit 2 continuously operates to receive a response signal. However, when no response signal is detected within a counting time of portable unit timer 28, operational area out alarm generation section 27 is activated under the control of portable unit control circuit 24 to perform an operation of notifying that portable unit 2 is outside of the operational area.

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates to a telephone instrument, and more particularly to a cordless telephone instrument. 2. Description of the Related Arts A cordless telephone instrument is constituted from a fixed unit and a portable unit connected to the fixed unit by way of a radio channel. With the cordless telephone instrument, service can be performed between the fixed unit and the portable unit while the portable unit is being moved within an area within which the fixed unit and the portable unit can be connected to allow operation between them through the radio channel, that is, within an operational area. Accordingly, when the portable unit is moved outside the operational area, connection between the fixed unit and the portable unit through the radio channel is disabled and a call through a telephone line by the portable unit becomes disabled. Therefore, in some conventional cordless telephone instruments, an alarm is developed when it is detected during talking that the portable unit has moved out of the operational area, as disclosed in Japanese Patent Application Laid-Open No. Heisei 3-114338 or 3-114339. In some other conventional cordless telephone instruments, if no response is received from a fixed unit when the portable unit tries to originate a call, it is determined that the portable unit is outside the operational area, and an alarm is developed. Further, in some other conventional cordless telephone instruments, if no response is received from a portable unit within a predetermined period of time another more propagative call signal is developed from the fixed unit, as disclosed in Japanese Patent Application Laid-Open No. Heisei 3-13040. U.K Patent Appln. 2,257,332 (Rose et al.) discloses a digital cordless telephone apparatus in which a link check command signal is periodically transmitted by a base unit and acknowledged by a handset unit to evaluate the quality of the communication link between the two and determine if an out-of-range condition exists. U.S. Patent 4,853,951 (Bauer) discloses a cordless telephone with in-range monitoring, in which a user of a handset can initiate a verification signal to a fixed station, which then verifies the received signal and sends back an acknowledgment signal with a number and code of the verification signal; a warning is given to the handset user if the acknowledgment signal is not received. In this manner, various cordless telephone instruments wherein it is displayed by way of an alarm whether the portable unit is positioned within the operational area have conventionally been proposed. However, with the cordless telephone instruments of the type described, since determination whether or not the portable unit is positioned within the operational area is performed during talking or call originating operation or call receiving operation, it is not able to notify to the user whether the telephone service is available when the cordless telephone instrument is in a state of on-hook which occupies the major part in normal state. Accordingly, it sometimes occurs that, while the cordless telephone instrument is not in use, the portable unit is carried to a location outside the operational area and cannot originate a call at the location, or since the portable unit is outside the operational area upon reception of a call, the reception of a call is not known to the user, resulting in a miss of the timing to respond. In this manner, when the portable unit should be used, sometimes it actually cannot be used. Consequently, the conventional cordless telephone instruments described above are disadvantageous to enjoy sufficiently the merit of a cordless telephone instrument such that the portable unit can be freely carried and used within a certain area. SUMMARY OF THE INVENTION It is an object of the present invention to provide a method of indicating a sign when a portable unit of a cordless telephone instrument moves out of its operational area by way of an alarm even when the cordless telephone instrument is in a state of on-hook, and a cordless telephone instrument to which the method is applied. In order to attain the object described above, according to a first aspect of the present invention, there is provided a method of indicating that a portable unit of a cordless telephone instrument which comprises a fixed unit and a portable unit is out of operational area, comprising the steps of: starting counting of a predetermined first reference time at the portable unit; transmitting a registration signal of a first frequency peculiar to the cordless telephone instrument from the portable unit after lapse of the first reference time and starting next counting of the first reference time by the portable unit; transmitting, upon reception of the registration signal by a fixed unit, a response signal of a second frequency peculiar to the fixed unit; resetting, when the portable unit having transmitted the registration signal receives the response signal, the counted value of the first reference time, and starting next counting of the first reference time by the portable unit; and, outputting, when said portable unit receives no response signal after lapse of more than a predetermined third reference time longer than the first reference time after having transmitted the registration signal, an indication of an unavailable situation on the portable unit. According to a second aspect of the present invention, there is provided a cordless telephone instrument which includes a fixed unit, and a portable unit connected to the fixed unit through a radio channel, comprising: portable unit timer means provided in the portable unit for counting, every time after the portable unit timer means is reset, a predetermined first reference time and outputting a time-out signal when said portable unit timer means counts up the first reference time; transmission and reception means provided in the portable unit for transmitting, every time the time-out signal is outputted, a registration signal of a first frequency peculiar to the cordless telephone instrument toward the fixed unit and receiving a response signal from said fixed unit; means provided in the portable unit for resetting the portable unit timer means when the response signal is received; means provided in the portable unit for outputting an indication of an unavailable situation on the portable unit when the response signal is not received within the first reference time; and means provided in the fixed unit for sending out, when a registration signal is received from the portable unit, a response signal of a second frequency peculiar to the subscriber toward said portable unit. Also, the cordless telephone instrument wherein the means for outputting an indication of an unavailable situation is an alarm generation section for outputting an alarming sound, and a display of an alarm indication mark simultaneously, is included in the present invention. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a block diagram of an embodiment of a cordless telephone instrument of the present invention; and Fig. 2 is a flow chart illustrating operation of the embodiment of Figure 1. DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention are described below with reference to the drawings. Fig. 1 is a block diagram of a first embodiment of a cordless telephone instrument of the present invention. Fixed unit 1 is installed fixedly at an appropriate location and connected to telephone line 3. Meanwhile, portable unit 2 is formed as a cordless portable unit. Portable unit 2 is moved at any time by its user and is placed at an indefinite location when it is not used. Portable unit 2 is connected to fixed unit 1 through radio channel 4. As a result, portable unit 2 is connected to telephone line 3 by way of fixed unit 1 so that service can be enjoyed. In this instance, radio channel 4 is constituted from a radio section 12 of fixed unit 1 and radio section 21 of portable unit 2, and the transmittable distance of radio waves between fixed unit 1 and portable unit 2 limits the range of movement of portable unit 2. Fixed unit 1 includes known telephone circuit 11 connected to a telephone line, fixed unit radio circuit 12 for connecting a signal of telephone circuit 11 to portable unit 2 through radio channel 4, response signal generation circuit 14 for generating a response signal of a frequency allocated to the cordless telephone instrument, and fixed unit control circuit 13 for controlling telephone circuit 11, fixed unit radio section 12 and response signal generation circuit 14. Meanwhile, portable unit 2 includes portable unit radio section 21 for establishing radio connection to fixed unit 1, transmitter 22 and receiver 23 connected to portable unit radio section 21, key section 25 including a switch and a dial which are operated when portable unit 2 is used, indication section 26 for indicating that portable unit 2 is unavailable, operational area out alarm generation section 27 for generating an unavailable condition indicating alarming sound when portable unit 2 has moved out of the operational area, portable unit timer 28 for counting a predetermined time every time after it is reset, registration signal generation circuit 29 for generating a registration signal of the peculiar frequency allocated to the cordless telephone instrument, and portable unit control circuit 24. Operation of the first embodiment having the construction described above for determining that the portable unit is out of the operational area while the cordless telephone instrument is in a state of on hook is described. Fig. 2 is a flow chart of operation of the first embodiment. While portable unit 2 is in a state of on hook (step 31), portable unit timer 28 counts and sets a first time when operated, and for each time-out of portable unit timer 28 (step 32), portable unit timer 28 outputs a time-out signal to portable unit control circuit 24. After the time-out signal is received, portable unit control circuit 24 controls portable unit radio section 21 to transmit a registration signal outputted from registration signal generation circuit 29 toward fixed unit 1 (step 33). Since fixed unit 1 can receive the registration signal from portable unit 2 while portable unit 2 is within the operational area, when the signal from portable unit 2 is received through fixed unit radio section 12, fixed unit control circuit 13 determines whether or not the received signal is the registration signal (step 34). If fixed unit control circuit 13 determines that the received signal is a registration signal, then fixed unit control circuit 13 controls fixed unit radio section 12 to transmit a response signal outputted from response signal generation circuit 14 toward portable unit 2 (step 35). Meanwhile, portable unit control circuit 24 supervises reception of a response signal by portable unit radio section 21 for a predetermined time after each transmission of the registration signal (step 36). If reception of a response signal is detected within the time, portable unit control circuit 24 sends out a reset signal to portable unit timer 28 to reset portable unit timer 28 so as to re-start counting of time by the portable unit timer 28 (step 38). In this instance, operation area out alarm generation section 27 is not activated. In this case, it may be able to indicate by indication section 26 that portable unit 2 is within the operational area. On the other hand, if portable unit 2 has moved out of the operational area, the registration signal transmitted from portable unit radio section 21 cannot be received by fixed unit 1 any more, and consequently, fixed unit 1 does not transmit a response signal. Accordingly, since portable unit 2 receives no response signal within the predetermined time, portable unit timer 28 is not reset but outputs a time-out signal (step 40). Portable unit control circuit 24 activates operational area out alarm generation section 27 in response to the time-out signal to generate alarming sound (step 41). Further, it simultaneously indicates by indication section 26 that portable unit 2 is out of the operational area. Consequently, even when the cordless telephone instrument is in a state of on hook, the user can acknowledge that the portable unit is out of the operational area but is available for call origination and reception of call. For a case where recognition whether or not portable unit 20 has moved out of the operational area is not required, the cordless telephone instrument may be modified so as to have a switch for switching off only the unavailable condition display apparatus portion comprising portable unit control circuit 24, indication circuit 26, operational area out alarm generation section 27, portable unit timer 28 for portable unit 20 and registration signal generation circuit 29 additionally for portable unit 2. Each feature disclosed in this specification (which term includes the claims) and/or shown in the drawings may be incorporated in the invention independently of other disclosed and/ or illustrated features.

Claims: A method of indicating that a portable unit (2) of a cordless telephone instrument which comprises a fixed unit (1) and a portable unit (2) is out of operational area, comprising the steps of: starting counting (32) of a predetermined first reference time at said portable unit; transmitting (33) a registration signal of a first frequency peculiar to said cordless telephone instrument from said portable unit after lapse of the first reference time, and starting a new count of the first reference time by said portable unit; transmitting (35), upon reception of the registration signal by a fixed unit, a response signal of a second frequency peculiar to said fixed unit; resetting (37), after said portable unit has received the response signal to the transmitted registration signal, the counted value of the first reference time and starting a new count of the first reference time by said portable unit; and outputting (41), when said portable unit receives no response signal after a lapse of more than a predetermined third reference time longer than the first reference time after having transmitted the registration signal, an indication of an unavailable situation on said portable unit. A cordless telephone instrument which includes a fixed unit (1), and a portable unit (2) connected to said fixed unit (1) through a radio channel, comprising: portable unit timer means (28) provided in said portable unit (2) for counting, every time said portable unit timer means is reset, a predetermined first reference time and outputting a time-out signal when said portable unit timer means counts up to the first reference time; transmission (22) and reception (23) means provided in said portable unit for transmitting, every time the time-out signal is outputted, a registration signal of a first frequency peculiar to said cordless telephone instrument toward said fixed unit (1), and receiving a response signal from said fixed unit; means (24) provided in said portable unit (2) for resetting said portable unit timer means (28) when the response signal is received; means (26, 27) provided in said portable unit (2) for outputting an indication of an unavailable situation on the portable unit when the response signal is not received within the first reference times; and, means (16) provided in said fixed unit (1) for sending out toward said portable unit (2), when a registration signal is received from said portable unit (2), a response signal of a second frequency peculiar to the subscriber. A cordless telephone as claimed in claim 2, wherein said means for outputting an indication of an unavailable situation is an alarm generation section (27) for outputting an alarm sound. A cordless telephone instrument as claimed in claim 2, wherein said means for outputting an indication of an unavailable situation is a display (26) of an alarm indication mark. A cordless telephone instrument as claimed in claim 2, wherein said means for outputting an indication of an unavailable situation is means for outputting an alarm sound (27) and simultaneous display (26) of an indication mark.

Inventors: SHIMURA YUKIHIRO, SHIMURA, YUKIHIRO, SHIMURA, YUKIHIRO, C/O NEC CORPORATION
Applicants: NIPPON ELECTRIC CO, NEC CORPORATION
Application year: 1995
Main classification: H04M1
IPC codes: H04M1, H04Q7