The patent badge is an abbreviated version of the USPTO patent document. The patent badge does contain a link to the full patent document.
The patent badge is an abbreviated version of the USPTO patent document. The patent badge covers the following: Patent number, Date patent was issued, Date patent was filed, Title of the patent, Applicant, Inventor, Assignee, Attorney firm, Primary examiner, Assistant examiner, CPCs, and Abstract. The patent badge does contain a link to the full patent document (in Adobe Acrobat format, aka pdf). To download or print any patent click here.
Patent No.:
Date of Patent:
Mar. 13, 1990
Filed:
Jan. 22, 1988
James P Santos, Larchmont, NY (US);
Other;
Abstract
Two miniaturized transceivers, each selectively responsive to predetermined radio frequency (r.f.) transmissions which may be coded, consisting of one control unit and one transponder unit. Transmission by the control unit of a modulated frequency which is received and decoded by the transponder will generate a like reply from the transponder whose round-trip delay is timed and because of the known velocity of radio waves can thus be displayed as the distance between the two units. An adjustable maximum range limit in the control unit will generate an audible, visual or other alerting signal in the control unit when the distance between the two units is exceeded. Such signal is also obtained when the signal from the transponder is interrupted. Low-power consumption can be effected for battery operation by arranging short periodic bursts of r.f. energy between the two transceivers, there being logical means to time-align the respective transmit and receive modes of the two units. The transponder transceiver can be considered as behaving like an 'active' reflector of the predetermined r.f. signals from the control unit.