Chao Liu

US Patent:

41907477, Feb 26, 1980

Filed:

Apr 5, 1978

Appl. No.:

5/893795

Inventors:

Alexander Feiner - Rumson NJ
Chao Kai Liu - Matawan NJ
Sigurd G. Waaben - Princeton NJ

Assignee:

Bell Telephone Laboratories, Incorporated - Murray Hill NJ

International Classification:

H04B 158
H04B 900

US Classification:

179170NC

Abstract:

A remote gain controlled optocoupled device is disclosed utilizing a DC reference voltage in the output section to compensate for variations in the optocoupling characteristics of the circuit. The DC voltage level output of the photodetector, which is a function of the light transfer characteristics of the circuit, is compared to a remotely controlled reference DC level. The output AC signal level, which substantially tracks the DC voltage output, is gain adjusted under control of the compared DC voltage levels.

US Patent:

39912809, Nov 9, 1976

Filed:

May 23, 1975

Appl. No.:

5/580293

Inventors:

Dennis Bryan James - Rumson NJ
Chao Kai Liu - Matawan NJ
Robert McKee Smith - Holmdel NJ

Assignee:

Bell Telephone Laboratories, Incorporated - Murray Hill NJ

International Classification:

H04M 356

US Classification:

179 18BC

Abstract:

In order to reduce the signal loss in a telephone line switching and conferencing system there is interposed between each line and the switching matrix a monobus port circuit arranged to convert a transmitted telephone signal into an equivalent current source. The currents from several monobus circuits are added in a bus resistor before distribution back to the individual monobus circuit where the original signal is subtracted from the bus signal. The resultant signal is transmitted to the telephone receiver. When the switching matrix crosspoint resistance is negligible, the component of the bus voltage measured at the current source output which results from current generated from each line is equal and opposite in magnitude to the voltage generated in the line. In any given line these voltages cancel each other, thereby eliminating the feedback signal. In situations where it is desired to use crosspoints having an unknown resistance, the voltage returned from the monobus does not exactly match the locally generated voltage because of the voltage drop across the crosspoint and thus a feedback signal of unknown magnitude is applied to the telephone line.

US Patent:

39900606, Nov 2, 1976

Filed:

Mar 27, 1974

Appl. No.:

5/455425

Inventors:

Yeong S. Lin - Mount Kisco NY
Chao N. Liu - Yorktown Heights NY
Donald T. Tang - Yorktown Heights NY

Assignee:

International Business Machines Corporation - Armonk NY

International Classification:

G11C 1114
G11C 1908

US Classification:

340174TF

Abstract:

The data stored in a coincident block access bubble domain memory with bit-organized chips is encrypted by skewing or permuting selected word bits by predetermined amounts. This is implemented by providing an additional current loop on some or all of the chips which overlies the major loop pattern and has nodes at the similar vector poles of the major loop. The proper energization of selected ones of these additional current loops, under the control of a security key, inhibits or suppresses the advance of the bubble domains in the corresponding major loops for a predetermined number of cycles of the in-plane propagating field, thus skewing the word bits in these chips with respect to the remaining word bits in the unsuppressed chips. Decryption is accomplished by further inhibiting the same major loops for the necessary number of cycles to restore word bit synchronization throughout the memory.

US Patent:

41288297, Dec 5, 1978

Filed:

Dec 30, 1977

Appl. No.:

5/866190

Inventors:

Noel M. Herbst - Mount Kisco NY
Chao N. Liu - Yorktown Heights NY

Assignee:

International Business Machines Corporation - Armonk NY

International Classification:

G06K 910

US Classification:

3401463SY

Abstract:

Method and apparatus are disclosed for verifying a sample signature based on comparison of the dynamics of a reference and a sample signature. More particularly, second derivative values of pen displacements (i. e. acceleration) and continuous pressure pattern signals are periodically sampled for both a reference and sample signature and a comparison of these second derivative values and pressure patterns is made. To effect the comparisons the two groups (reference and sample) of both second derivative and pressure pattern signals are segmented and corresponding segments are individually correlated. Successive comparisons of the same segment pairs are performed utilizing successive shifting of the phases between the two segments being correlated to find regions of highest possible correlation. A running account of the maximum cross correlation values for all of the segment pairs of the two signatures are kept. Finally, these maximum values obtained for each segment pair comparison are combined and this resultant correlation value is utilized as a verification indicator.

US Patent:

41421752, Feb 27, 1979

Filed:

Jun 12, 1978

Appl. No.:

5/914651

Inventors:

Noel M. Herbst - Mount Kisco NY
Chao N. Liu - Yorktown Heights NY
Hugo A. Panissidi - Peekskill NY

Assignee:

International Business Machines Corporation - Armonk NY

International Classification:

G01L 516

US Classification:

3401463SY

Abstract:

A pressure sensing device having applicability as a simple pressure sensor and which is particularly adapted for use as a pen in a Signature Verification System, said device including a unique mounting structure for the pressure sensing stylus by flexible support means mounted on a substantially rigid base. The support means has a pressure sensing element mounted thereon. The flexible support means comprises two spaced members so disposed that their deflections and the output of the pressure sensing element are substantially independent of the angle of pressure on the stylus. In the special purpose embodiment useful for Signature Verification the stylus comprises a pen and the device further includes two orthogonally disposed accelerometers for sensing accelerations of said pen during the writing of a signature.

US Patent:

42283230, Oct 14, 1980

Filed:

Jan 31, 1979

Appl. No.:

6/008194

Inventors:

Alexander Feiner - Rumson NJ
Chao Kai Liu - Matawan NJ
Sigurd G. Waaben - Princeton NJ

Assignee:

Bell Telephone Laboratories, Incorporated - Murray Hill NJ

International Classification:

H04B 900

US Classification:

179 16F

Abstract:

A gain and frequency compensated barrier circuit is disclosed for use with a telephone transmission line having variable loop lengths. A DC component of the input signal is provided to the input side of the barrier circuit. Loop length losses, as well as barrier gain variations, are adjusted on the output side of the circuit by comparing a barrier DC voltage level with a DC reference level and adjusting the AC gain in accordance therewith. Frequency response, which is also a function of loop length, is corrected by using the DC input voltage to generate an effective loop length dependent capacitor for further controlling the output signal level. An optocoupled circuit is disclosed for use in one embodiment of the disclosure.

US Patent:

40456153, Aug 30, 1977

Filed:

May 21, 1976

Appl. No.:

5/688787

Inventors:

Dennis Bryan James - Rumson NJ
Chao Kai Liu - Matawan NJ
Douglas Charles Smith - Rumson NJ

Assignee:

Bell Telephone Laboratories, Incorporated - Murray Hill NJ

International Classification:

H04M 356

US Classification:

179 1CN

Abstract:

In order to reduce the signal loss in a telephone line switching and conferencing system there is interposed between each line and the switching matrix a monobus port circuit arranged to convert a transmitted telephone signal into an equivalent current source. An opto-coupled hybrid replaces the port circuit transformer and serves to provide the desired voltage to current conversion. The currents from several monobus circuits are added in a bus resistor before distribution back to the individual monobus circuits as a voltage where the original signal is subtracted from the bus signal. The resultant signal is transmitted to the telephone receiver via the opto-coupled hybrid. When the switching matrix crosspoint resistance is negligible, the component of the bus voltage measured at the current source output which results from current generated from each port circuit is equal and opposite in magnitude to the voltage generated in the port circuit. In any given line these voltages cancel each other, thereby eliminating the feedback signal.