Communications: electrical – Continuously variable indicating – With meter reading
Patent
1986-07-07
1987-04-14
Weldon, Ulysses
Communications: electrical
Continuously variable indicating
With meter reading
34082534, 235435, 235439, G09C 100
Patent
active
046582525
ABSTRACT:
A surface acoustic wave (SAW) filter device configured as a tapped time delay is mounted on a plastic card. The SAW filter acts as a nondestructive storage medium for an identification code in an access control system. The identification code is imbedded in the SAW device by selectively connecting certain taps to the filter output terminals. The identification code is read out of the SAW filter device and decoded for verification of the code. To read the code a sweep frequency oscillator excites the filter to launch an acoustic wave. The filter ouput mixes with the input sweep signal and the lower sideband (f.sub.b -f.sub.a) is extracted to obtain a discrete line spectra each line representing the connected tap of the filter. The line spectra signal is mixed with another version of the input sweep signal to obtain a time-based amplitude response of the discrete line spectra. This analog signal is converted to a digital signal which corresponds to the binary code of the connections to the SAW filter.
REFERENCES:
patent: 3344629 (1967-10-01), Burney
patent: 3377616 (1968-04-01), Auer
patent: 3568102 (1971-03-01), Tseng
patent: 3706094 (1972-12-01), Cole et al.
patent: 3836876 (1974-09-01), Marshall et al.
patent: 4006436 (1977-02-01), Heeks
patent: 4058217 (1977-11-01), Vaughan et al.
Gilbert Douglas M.
GTE Government Systems Corporation
Weldon Ulysses
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