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:
Jul. 14, 1987
Filed:
Sep. 17, 1984
Marshall H Martin, Northridge, CA (US);
Indicator Controls Corporation, Gardena, CA (US);
Abstract
A microprocessor controlled loop detection system to be connected to a number of inductive loops which are buried in a road bed and which is used to detect the presence of motor vehicles above the loops to control the operation of traffic lights at an intersection. A common oscillator is connected to each loop on a time-shared basis under the control of a microprocessor, and the frequency of the oscillator in each instance is dependent upon whether or not there is a vehicle above the loop. The microprocessor provides a null time as the system is switched from one loop to another to prevent spurious responses in the system due to transient signals. The microprocessor acts to count the number of cycles of the output signal of the oscillator which occur during a predetermined time interval as each loop is connected to the oscillator by the microprocessor to determine the oscillator frequency for each loop and thereby detect the presence of a vehicle in the particular loop. A synchronizing circuit is provided connecting the oscillator to the microprocessor for controlling the start and finish of each such counting interval by the microprocessor.