| (19) |
 |
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(11) |
EP 0 301 812 A3 |
| (12) |
EUROPEAN PATENT APPLICATION |
| (88) |
Date of publication A3: |
|
12.07.1989 Bulletin 1989/28 |
| (43) |
Date of publication A2: |
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01.02.1989 Bulletin 1989/05 |
| (22) |
Date of filing: 26.07.1988 |
|
| (51) |
International Patent Classification (IPC)4: G08G 1/01 |
|
| (84) |
Designated Contracting States: |
|
AT BE CH DE ES FR GB GR IT LI LU NL SE |
| (30) |
Priority: |
27.07.1987 US 77933
|
| (71) |
Applicant: DETECTOR SYSTEMS INC. |
|
Stanton
California 90860 (US) |
|
| (72) |
Inventor: |
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- Potter, Thomas Ray
Los Alamitos California 90720 (US)
|
| (74) |
Representative: Beresford, Keith Denis Lewis et al |
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BERESFORD & Co.
2-5 Warwick Court
High Holborn
London WC1R 5DJ
London WC1R 5DJ (GB) |
|
| |
|
| (54) |
Improved vehicle detector method and system |
(57) In an inductive loop vehicle detector, a sample count which depends on the loop inductance
is compared with a reference count in producing a detection signal. In order to take
account of loop drift, the reference count is replaced with the sample count when
the difference therebetween indicates drift for a predetermined period of time.