diff --git a/slides/lectures/acs_cc/04/slides.md b/slides/lectures/acs_cc/04/slides.md
index 9b8c08a24..b1a6fbe9f 100644
--- a/slides/lectures/acs_cc/04/slides.md
+++ b/slides/lectures/acs_cc/04/slides.md
@@ -40,12 +40,6 @@ Lecture 4
src: ../../resources/timers/slides.md
---
-
-
----
-src: ../../resources/signals/slides.md
----
-
---
diff --git a/slides/lectures/fils_en/04/slides.md b/slides/lectures/fils_en/04/slides.md
index 6b86d0fd4..f91aa7c9b 100644
--- a/slides/lectures/fils_en/04/slides.md
+++ b/slides/lectures/fils_en/04/slides.md
@@ -43,7 +43,7 @@ src: ../../resources/timers/slides.md
---
-src: ../../resources/signals/slides.md
+src: ../../resources/signals/basic.md
---
diff --git a/slides/lectures/resources/signals/ICs_same_voltage.svg b/slides/lectures/resources/signals/ICs_same_voltage.svg
new file mode 100644
index 000000000..0c0d273d3
--- /dev/null
+++ b/slides/lectures/resources/signals/ICs_same_voltage.svg
@@ -0,0 +1 @@
+
\ No newline at end of file
diff --git a/slides/lectures/resources/signals/VCC1_smaller_VCC2.svg b/slides/lectures/resources/signals/VCC1_smaller_VCC2.svg
new file mode 100644
index 000000000..73256f1f9
--- /dev/null
+++ b/slides/lectures/resources/signals/VCC1_smaller_VCC2.svg
@@ -0,0 +1 @@
+
\ No newline at end of file
diff --git a/slides/lectures/resources/signals/basic.md b/slides/lectures/resources/signals/basic.md
new file mode 100644
index 000000000..25334be4f
--- /dev/null
+++ b/slides/lectures/resources/signals/basic.md
@@ -0,0 +1,68 @@
+---
+layout: section
+---
+# Signals
+Digital Signals - Recap
+
+---
+
+# Signals
+Analog vs Digital
+
+
+
+
+
+- *analog signals* are *real* signals
+- *digital signals* are *a numerical representation* of an analog signal (software level)
+- hardware usually works with two-level digital signals (hardware level)
+
+#### Exceptions
+- in wireless and in high-speed cable communication things get more complicated
+
+> for PCB level / between integrated circuits on the same board / inside the same chip - things are a "a little simpler" - as detailed in the following
+
+
+
+
+
+
+
+---
+
+# Why use digital in computing?
+
+
+
+
+
+Signal that we *want* to generate with an output pin
+
+
+
+
+
+
+
+
+Signal that what we actually generate
+
+
+
+
+
+
+
+> Why we sill use it? Because after passing through an IC or a gate inside an IC - the signal si "rebuilt" and if the "digital discipline" described in the following is respected - we can preserve the information after numerous "passes". Thus, each element can behave with a large margin for error, yet the final result is correct.
+
+---
+---
+# Noise Margin
+
+
+
+
+
+
+
+
diff --git a/slides/lectures/resources/signals/d_output.svg b/slides/lectures/resources/signals/d_output.svg
new file mode 100644
index 000000000..b707faf98
--- /dev/null
+++ b/slides/lectures/resources/signals/d_output.svg
@@ -0,0 +1 @@
+
\ No newline at end of file
diff --git a/slides/lectures/resources/signals/digital_v2.md b/slides/lectures/resources/signals/digital_v2.md
new file mode 100644
index 000000000..d46682d21
--- /dev/null
+++ b/slides/lectures/resources/signals/digital_v2.md
@@ -0,0 +1,14 @@
+---
+layout: section
+---
+# Digital Signals - recap & key points
+
+Recap from ED & key concepts usefull for PM
+
+
+
+---
+
+# Digital Signals - recap & key points
+
+#
diff --git a/slides/lectures/resources/signals/extra.md b/slides/lectures/resources/signals/extra.md
new file mode 100644
index 000000000..05755dfa9
--- /dev/null
+++ b/slides/lectures/resources/signals/extra.md
@@ -0,0 +1,191 @@
+---
+layout: two-cols
+---
+
+# Why is the output not ideal?
+
+
+### The two corresponding voltage output levels are affected by:
+
+- power supply voltage
+- output current
+- temperature
+- variations in the manufacturing process
+
+:: right ::
+
+
+
+
+
+
+
+
+
+---
+layout: two-cols
+---
+
+# ICs same voltage
+
+
+### Usually will work as is
+
+- usually, they will be compatible
+- conditions:
+> V_OH_transmiter > V_IH_receiver
+
+
+
+> V_OL_transmiter < V_IL_receiver
+
+:: right ::
+
+
+
+---
+layout: two-cols
+---
+
+# VCC1 > VCC2
+
+
+### Might work, might produce magic smock
+
+- if
+> V_OH_transmiter > VCC_receiver
+
+ PROBLEM
+
+### Solutions:
+- level shifter
+- resistor divider / voltage limiter
+
+Examples:
+
+
+ Bi-Directional Level Shifter (4 Channels)
+
+
+
+
+
+ Level Shifter Multi-Channel
+
+
+
+
+
+
+ 8 Channels Level Shifter
+
+
+
+
+
+:: right ::
+
+
+
+
+---
+layout: two-cols
+---
+
+# VCC1 < VCC2
+
+
+### Might work
+
+- if
+> V_CC_transmiter close to VIH_receiver
+
+ Might work in an intermittent mode - hard to debug!
+
+### Solutions:
+- level shifter
+- resistor divider / voltage limiter
+
+Examples:
+
+
+ Bi-Directional Level Shifter (4 Channels)
+
+
+
+
+
+ Level Shifter Multi-Channel
+
+
+
+
+
+
+ 8 Channels Level Shifter
+
+
+
+
+
+:: right ::
+
+
+
+
+---
+layout: two-cols
+---
+
+# Why Pull-Down R
+
+- Without pull-down – when the button is not pressed, it leaves the input pin floating.
+- The second design ensures that the voltage level has a well-defined state, regardless of the button's state.
+- R1 is called a "pull-down" resistor.
+
+:: right ::
+
+
+
+
+
+
+
+
+
+---
+layout: two-cols
+---
+
+# Why Pull-Up R
+
+- Same reasoning
+- R1 is called a "pull-up" resistor.
+
+##Obs:
+- most microcontrollers have at least a pull-up resistor incorporated on GPIOs - that can be activated in software
+- some have both pull-up and pull-down
+- typically, these are sized for a 50 - 10 nA current consumption
+
+
+:: right ::
+
+
+
+
+
+
+
+
+
+---
+
+# Notes on output pins
+
+- most microcontrollers have a limit of around 10mA per output PIN
+- ! do not connect an LED without a resistor in series )to limit the current)
+- ! do not connect a motor / any type of inductive load
+
+## Solutions:
+- use a transistor
+- use an IC with incorporated Darlinghtons (eg: ULN2003)
diff --git a/slides/lectures/resources/signals/pull_down.png b/slides/lectures/resources/signals/pull_down.png
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diff --git a/slides/lectures/resources/signals/vcc1_larger_vcc2.svg b/slides/lectures/resources/signals/vcc1_larger_vcc2.svg
new file mode 100644
index 000000000..ae8045887
--- /dev/null
+++ b/slides/lectures/resources/signals/vcc1_larger_vcc2.svg
@@ -0,0 +1 @@
+
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