TWO SCANNER PATENTS



by Bob Parnass, AJ9S



Here is the information I published a few years ago about

two of the scanner patents held by General Research Elec-

tronics (GRE), makers of most Radio Shack scanners. You can

find out this type of information by spending a few minutes

in your corporate or academic law library.



A Channel Lockout Invention



Almost every model scanner sold today provides a way to

bypass, or "lock out" channels from being scanned. It

wasn't always this way. The first Bearcat scanner, a crys-

tal controlled model with a row of red lights, had no

lockout provision.



On February 26, 1974, a U.S. patent was granted to a

Japanese citizen for a "frequency skipping system" for scan-

ning receivers. Patent 3,794,925 was granted to Kazuyoshi

Imazeki, of Tokyo for a "Frequency-Skipping System for a

Signal-Seeking Receiver."



Filed almost two years earlier, Imazeki's development was

described as a "switching network" operable "to cause the

scanning circuit to skip those frequencies which the opera-

tor does not want to monitor."



The need for a lockout circuit was evident: "in some situa-

tions the operator may not be interested in receiving one or

more of the channels. Unless some provision is made for

skipping these undesired channels, the system automatically

tunes the receiver to them whereupon the operator must

either listen to the undesired channel until it goes off the

air or manually advance the receiver to the next channel."



Earlier lockout schemes had drawbacks. The circuitry was

"relatively complex and expensive" and had "the further

disadvantage of requiring almost as much time to skip a

channel as that required to tune to, and through, that chan-

nel. In a system having ten or more channels of which only

two or three are of interest to a particular operator, a

relatively substantial amount of time is lost tuning through

the 'skipped' channels."



An example of this slower scheme was the way the Heathkit

GR-110 scanner accomplished lockout, by merely providing a

switch in series with each crystal.



In Imazeki's scheme, an extra clock pulse was applied to the

scanning counter circuit when a locked out channel was next

in the scan sequence. This innovation allowed faster scan-

ning of desired channels, by forcing the scanner to the next

channel.



The patent assignee is General Research of Electronics Inc.





Priority Scanning Scheme



It was 16 years ago last month that a U.S. patent was

granted to a Japanese citizen for a priority scheme for

scanning receivers. On April 2, 1974, patent 3,801,914 was

granted to Kazuyoshi Imazeki, of Tokyo for a "Priority-

Frequency System for a Signal-Seeking Receiver".



Filed almost two years earlier, the system provided for a

"signal seeking receiver to automatically tune" ... "to a

priority signal whenever it is received. During non-

priority receiver operation, a scanning circuit causes the

receiver to automatically scan a plurality of predetermined

frequencies and tune to a received signal have a frequency

corresponding to one of the predetermined frequencies."



In Imazeki's scheme, a low frequency priority oscillator

periodically halts the scanner's clock circuit, interrupting

the normal scan sequence. The priority oscillator's output

is also connected through a multi-position switch, which

allowed the user to designate an arbitrary channel as the

priority channel.



The circuit diagram in the patent looks familiar. That's

because it forms the basis for the priority feature found in

many crystal controlled scanners. The assignee is General

Research of Electronics Inc.

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Bob Parnass, AJ9S - AT&T Bell Laboratories - att!ihuxz!parnass (708)979-541


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