replace system_model submodule w/ directory (#51)

- update symbolic links to point to system_model folder in project-tetra-docs root directory

.gitmodules

@@ -2,7 +2,3 @@
 [submodule "themes/docsy"]
 	path = themes/docsy
 	url = https://github.com/google/docsy
-[submodule "src"]
-	path = src
-	url = https://github.com/helpfulengineering/project-tetra.git
-	update = merge

content/en/explanations/overview/system_model

@@ -1 +1 @@
-../../../../src/system_model
+../../../../system_model

content/en/explanations/system_model

@@ -0,0 +1 @@
+../../../system_model

content/en/references/system_model

@@ -1 +1 @@
-../../../src/system_model
+../../../system_model

system_model/block-ventilator-splitter-assembly.puml

@@ -0,0 +1,18 @@
+@startuml
+
+component "<b>Inspiratory Section</b>" <<block>> as vsbIn
+component "<b>Expiratory Section</b>" <<block>> as vsbOut
+interface "<b>Inspiratory Port</b>" as vsbpIn
+interface "<b>Expiratory Port</b>" as vsbpOut
+
+component "<b>Bias Circuit P/N</b>" <<bias circuit>> as bc
+
+component "<b>1-Way Valve P/N</b>" <<1-Way valve>> as vIn1
+component "<b>Flow Control P/N</b>" <<flow control>> as fcIn1
+component "<b>Shutoff valve P/N</b>" <<shutoff valve>> as sIn1
+
+component "<b>1-Way Valve P/N</b>" <<1-Way valve>> as vOut1
+component "<b>Pressure sensor P/N</b>" <<pressure sensor>> as psOut1
+component "<b>Shutoff valve P/N</b>" <<shutoff valve>> as sOut1
+
+@enduml

system_model/ibd-system-electronic-sensing-system-dataflow.puml

@@ -0,0 +1,73 @@
+@startuml
+left to right direction
+skinparam nodesep 100
+skinparam ranksep 100
+frame "ibd [System] Electronic Sensing System [Power and Data Flow]" {
+  [Raspberry Pi B+] <<Microcontroller>> as [Pi]
+  () "Wall Outlet" as WO
+
+  rectangle "Power System" {
+    [LM259SX-5] <<Voltage Regulator>> as [VR]
+    [Power Jack] as PJ
+    WO ..> PJ
+    PJ ..> VR
+    VR ..> Pi: 5V
+  }
+
+  together {
+    rectangle "Pressure Sensing System" as PresSens{
+      [SPL06 - 007 (x5)] <<Pressure Sensors>> as Pres
+      [TCA9548A] <<I2C Pressure Multiplexer>> as [MUX1]
+      Pres .. MUX1: <<I2C>>
+    }
+
+    rectangle "Open-Source Flow Sensing System"  as Open{
+      [Automotive Airflow Sensors (x4)] <<Generic Sensors>> as AAS
+      [TCA9548A] <<Analog Digital Converter>> as [ADC]
+      () "Automotive Airflow Connectors (x4)" as ACon
+      AAS -- ACon
+      ACon .. ADC: <<SPI>>
+    }
+
+    rectangle "FDA-Approved Flow Sensing System"  as FDA{
+      [Sensirion Airflow Sensors (x4)] <<Sensirion Sensors>> as Sens
+      [TCA9548A] <<I2C Flow Multiplexer>> as [MUX2]
+      () "Sensirion Airflow Connectors (x4)" as SCon
+      Sens -- SCon
+      SCon .. MUX2: <<I2C>>
+    }
+  }
+
+  'Used for aligning boxes'
+  /'
+  PresSens -[hidden]-> FDA
+  FDA --> Open
+  '/
+
+  "Clinician" <<Human>> as Doc
+  "Patient" <<Human>> as Pat
+
+  Pat ..> Sens
+  Pat ..> Pres
+  Pat ..> AAS
+
+
+  MUX2 ..> Pi
+  ADC  ..> Pi
+  MUX1 ..> Pi
+
+  rectangle "Clinical Feedback" {
+      () "Raspberry Pi B+ Display" <<Display>> as Display
+      () "Indicator LEDs (x8)" as LED
+      () "Audio Alarm"  as Aud
+  }
+
+  Pi ..> LED
+  Pi ..> Aud
+  Pi ..> Display
+
+  LED ..> Doc
+  Aud ..> Doc
+  Display ..> Doc
+}
+@enduml

system_model/ibd-system-ventilator-splitter-assembly-airflow.puml

@@ -0,0 +1,52 @@
+@startuml
+left to right direction
+skinparam linetype polyline
+/'
+skinparam linetype ortho
+'/
+
+frame "ibd [System] Ventilator Splitter Assembly [Air flow] " {
+
+  actor "<b>patient</b>" <<human>> as patient
+
+  component "<b>LTV-1200</b>" <<ventilator>> as ventilator {
+    interface "<b>Expiratory Port</b>" as pOut
+    interface "<b>Inspiratory Port</b>" as pIn
+  }
+
+  component "<b>Inspiratory Arm P/N</b>" <<Inspiratory Arm>> as armIn
+  component "<b>Expiratory Arm P/N</b>" <<Expiratory Arm>> as armOut
+
+  pOut <.. armOut
+  pIn ..> armIn
+
+  component "<b>Ventilator Splitter Assembly</b>" <<block>> as vsb {
+    !include system_model/block-ventilator-splitter-assembly.puml
+
+    vsbpOut -- vsbOut
+    vsbpIn -- vsbIn
+    vsbOut <. bc
+    bc <. vsbIn
+
+    vsbIn ...> vIn1
+    vIn1 ..> fcIn1
+    fcIn1 ..> sIn1
+
+    vsbOut <... vOut1
+    vOut1 <.. psOut1
+    psOut1 <.. sOut1
+  }
+
+  armIn ..> vsbpIn
+  armOut <.. vsbpOut
+
+  component "<b>Inspiratory Arm to patient P/N</b>" <<Inspiratory Arm>> as arm2patIn
+  component "<b>Expiratory Arm to patient P/N</b>" <<Expiratory Arm>> as arm2patOut
+
+  sIn1 ..> arm2patIn
+  arm2patIn ..> patient
+
+  sOut1 <.. arm2patOut
+  arm2patOut <.. patient
+}
+@enduml