Synchronous receiving/transmitting departure alarm

• US 5,774,054 A
• Filed: 11/04/1996
• Issued: 06/30/1998
• Est. Priority Date: 11/04/1996
• Status: Expired due to Fees

• Current Assignee: E Lead Electronic Company Limited
• Original Assignee: E Lead Electronic Company Limited
• Inventors: Chen, Stephen
• Primary Examiner(s): Hofsass, Jeffery
• Assistant Examiner(s): Huang, Sihong
• Application Number:
  US08/743,079
• Time in Patent Office: 603 Days
• Field of Search: 340/572, 340/573, 340/825.49, 340/539, 455/343, 379/37
• US Class Current: 340/572.1
• CPC Class Codes: G08B 13/1427 with transmitter-receiver for distance detection
• CPC Class Codes: G08B 21/0227 System arrangements with a plurality of child units
• CPC Class Codes: G08B 21/023 Power management, e.g. system sleep and wake up provisions

Abstract

A synchronous receiving/transmitting departure alarm including a receiver unit and at least one transmitter unit cooperating with the receiver unit. Once a holder of the transmitter unit is far away from the holder of the receiver unit by a preset distance, the holder of the receiver unit can be in time warned. The transmitter unit intermittently transmits a clock pulse signal and a receiving circuit of the receiver unit is synchronously opened to receive the signal so as to judge whether the holder of the transmitter unit is within the preset distance. Therefore, a person under care or an article with the transmitter unit is prevented from missing or being lost. A mobile phone can be used with the alarm to inform the holder of the receiver unit of a phone call.

Claims

1. A synchronous receiving/transmitting departure alarm comprising at least one transmitter unit and a receiver unit, wherein:

the transmitter unit includes a pulse control circuit, a clock crystal, a transmitting circuits and an antenna which form a means for transmitting pulse signals at fixed time intervals; and

the receiver unit includes an antenna, a receiving circuit, a control circuit, a clock crystal, a receiving circuit controller, and a sound emitter or vibrating body which form a means for receiving said pulse signals and synchronizing said receiver and transmitter so that during the intervals between said pulse signals, the receiving circuit of the receiver unit is synchronously deactivated and before a next transmitted pulse signal is to be received the receiving circuit is again activated for receiving the next pulse signal from the transmitter unit, and whereby when the receiving circuit fails to receive the transmitted pulse signal once or continuously several times, the receiver unit by way of sound or vibration warns a holder of the receiver unit of the failure to receive the transmitted pulse signal, and

wherein the transmitter unit further includes an electromagnetic wave detecting circuit responsive to detection of an electro-magnetic wave for changing or stopping transmission of said pulse signals to thereby cause said receiving unit to warn the holder by sound or vibration that an electro-magnetic wave has been detected.

2. The alarm as claimed in claim 1, further comprising a detecting circuit in the transmitter unit, said detecting circuit being triggered by a button disposed on the transmitter unit so as to change or stop transmission of the pulse signals and thereby cause the receiver to warn the holder that the button has been pressed and that a carrier of the receiver unit is in need of rescue.

3. The alarm as claimed in claim 1, wherein the electro-magnetic wave detective circuit is a phone call detector disposed in the transmitter unit, whereby the transmitter unit causes the receiver unit to generate a sound or vibration to inform the holder of the receiver unit of the phone call.

4. The alarm as claimed in claim 1, wherein the receiver unit cooperates with more than one transmitter unit at the same time.