Daisy chain multiplexer

• US 5,123,015 A
• Filed: 12/20/1990
• Issued: 06/16/1992
• Est. Priority Date: 12/20/1990
• Status: Expired due to Fees

• Current Assignee: Rockwell International Corporation
• Original Assignee: Hughes Aircraft Company (Rtx Corporation)
• Inventors: Brady, Kenneth A. Jr., Sklar, Richard E.
• Primary Examiner(s): Olms, Douglas W.
• Assistant Examiner(s): Jung, Min
• Application Number:
  US07/630,713
• Time in Patent Office: 544 Days
• Field of Search: 370/112, 370/105.1, 370/85.7, 370/95.1, 370/99
• US Class Current: 370/539
• CPC Class Codes: B64D 11/0015 Arrangements for entertainment or communications, e.g. radio, television
• CPC Class Codes: B64D 11/00155 Individual entertainment or communication system remote controls therefor, located in or connected to seat components, e.g. to seat back or arm rest
• CPC Class Codes: H04J 3/047 Distributors with transistors or integrated circuits
• CPC Class Codes: H04J 3/1647 Subrate or multislot multiplexing

Abstract

Each unit of a daisy chain of separate and independent multiplexing units (10,12,14) is arranged to accept a group of local audio inputs (Audio 1-Audio 8) and an additional input (18,20,22) from a prior unit in the chain to time division multiplex the additional input with the local units. Each unit provides a single serial bit stream output (20,22,24) which comprises the additional input to the next identical multiplexer unit in the chain. The next multiplexer unit time division multiplexes all of its inputs to provide a single output which includes a serial presentation of its own local inputs and the local inputs of the preceding multiplexer unit of the chain. This single serial output of the next multiplexer next forms the additional input of a still further multiplexer unit of the chain, which itself may have its own local inputs. The third multiplexer unit provides a single output that is a serial presentation of the local inputs of all three multiplexers. Additional multiplexer units can be added to the chain as may be necessary or desirable to accommodate reconfiguration of systems with which the multiplexers are used.

Claims

1. A chain of multiplexers comprising:

first and second multiplexer units,

said first multiplexer unit having a plurality of local inputs and an output,

said second multiplexer unit having a plurality of second unit local inputs and having a remote input connected to receive the output of said first multiplexer unit,

said first multiplexer unit including;

timing means for generating frame sync signals establishing a repetitive frame divided into plurality of subframes,

means in said first multiplexer unit for time division multiplexing said input signals and assigning all of said input signals to individual time slots in a selected one of said subframes, a second one of said subframes having no signals assigned thereto,

said first multiplexer unit having an output including signals of said selected subframe and bearing frame sync signals, said second multiplexer unit including;

means for multiplexing said second unit local inputs with the remote input from the output of said first multiplexer unit,

second timing means for establishing a second multiplexer timing frame based upon said frame sync signals of said first multiplexer unit output, said second multiplexer timing frame having said plurality of subframes,

said second timing means including means for assigning signals contained in the output of said first multiplexer unit to said selected one of said subframes and for assigning said second unit local inputs to said second one of said subframes to provide an output from said second multiplexer unit comprising said first multiplexer unit local inputs followed by said second unit local inputs.

2. The apparatus of claim 1 wherein said first and second multiplexer units are positioned at a distance from one another.

3. The apparatus of claim 1 further comprising:

a third multiplexer unit,

said third multiplexer unit having a plurality of third unit local inputs and having a remote input connected to receive the output of said second multiplexer unit,

wherein said means in said first multiplexer unit for time division multiplexing said input signals assigns all of said inputs to individual slots in a selected one of said subframes, a second and a third one of said subframes having no signals assigned thereto,

said third multiplexer unit including;

means for multiplexing said third unit local inputs with the remote input from the output of said second multiplexer unit,

third timing means for establishing a third multiplexer timing frame based upon said frame sync signals of said first multiplexer unit output, said third multiplexer timing frame having said plurality of subframes,

said third timing means including means for assigning signals contained in the output of said second multiplexer unit to said selected one of said subframes and for assigning said third local inputs to said third one of said subframes to provide an output from said third multiplexer unit comprising first multiplexer unit local inputs followed by said second unit local inputs followed by said third unit local inputs.

4. A method for time division multiplexing different groups of input signals comprising the steps of:

providing a first group of inputs,

time division multiplexing digitized samples of the signals of said first group of inputs in a train of repetitive time frames each divided into a plurality of subframes, each having a plurality of time slots,

assigning the digitized samples of said first group of inputs to respective time slots of first individual one of said subframes,

transmitting as a remote signal said repetitive time frames and the subframes of each frame with said digitized samples in said first individual subframe, and at least one other subframe having no digitized samples,

providing a second group of inputs,

establishing a train of repetitive time frames synchronized with said first mentioned train and subdivided into said plurality of subframes and time slots,

time division multiplexing said remote signal with said second group of inputs, said last mentioned step of multiplexing comprising;

assigning digitized samples of said remote signal to time slots of said first individual one of said subframes,

providing digitized samples of a second group of inputs and assigning them to time slots of a second individual one of said subframes, and

providing an output signal comprising said time frames with digitized samples in said first and second individual subframes.

5. The method of claim 4 wherein said multiplexers are positioned at mutually displaced locations.

6. The method of claim 4 wherein said first group of inputs comprises the output of a first signal source located at a first position, and said second group of inputs comprises the output of a second signal source located at a second position displaced from said first position, said step of performing said first mentioned multiplexing being carried out at a location adjacent said first signal source and said step of multiplexing said remote signal being carried out at a position closely adjacent the location of said second audio source.

7. A daisy chain multiplexing system comprising:

a first audio source providing a first group of local analog audio inputs,

a first multiplexer unit comprising;

a plurality of analog to digital converters each connected to uniquely receive a different one of said local analog audio inputs and to provide digitized samples of said local inputs,

an array of multiplexing switches connected to receive said digitized samples and provide a composite stream of said samples,

multiplexer timer means for generating frame sync and time slot signals for establishing a repetitive frame divided into at least first and second subframes, each said subframe having a plurality of time slots,

said timer means including means for assigning digitized samples of said local inputs to the time slots of said first subframes and for keeping time slots of said second subframe free of digitized samples,

means for combining the frame sync and time slot signals with said composite serial bit stream of samples from said multiplexing switches to provide a combined first multiplexer unit output,

a second audio source positioned at a location remote from said first audio source and providing a second group of local analog audio inputs,

a second multiplexer unit positioned adjacent said second audio source and comprising;

a second plurality of analog to digital converters each connected to receive a different one of said second local analog audio inputs, and to provide digitized samples thereof,

a second array of multiplexing switches connected to receive said digitized samples from said second plurality analog to digital converters, one of said second group of multiplexing switches being connected to receive said combined first multiplexer unit output, said switches being connected to provide a combined second multiplexer unit output,

second multiplexer timer means in said second multiplexer unit responsive to the frame sync and time slot signals of said first combined multiplexer unit output for establishing a repetitive frame and time slots therefor for said second multiplexer, said repetitive frame of said second multiplexer being subdivided into at least first and second subframes,

said second timer means including means for uniquely assigning digitized samples of the first group of local audio inputs from said first source to a first one of said subframes and for assigning the digitized samples of the second group of local analog audio inputs to said second subframe to provide said combined second multiplexer unit output including in each frame thereof digitized samples of said first group of audio inputs from said first source followed by digitized samples of said second group of audio inputs from said second source.

8. The daisy chain multiplexer of claim 7 including modulator means connected to said first mentioned multiplexing switches for modulating said combined first multiplexer unit output upon an RF carrier to provide an RF carrier output having modulated thereon digitized samples of the local inputs from said first audio source and frame sync signals.

9. The multiplexer of claim 8 wherein said second multiplexer unit includes demodulator means for demodulating said RF carrier output and extracting frame sync and time slot signals therefrom, said second timer means being responsive to said frame sync signal for establishing frame synchronization and time slot positions of the composite signal combined second multiplexer unit output.