diff --git a/lambda/Makefile b/lambda/Makefile
index 5cc8122..6d6b6b9 100644
--- a/lambda/Makefile
+++ b/lambda/Makefile
@@ -15,7 +15,7 @@
 ## If you've split your program into multiple .c / .h files, 
 ## include the additional source (in same directory) here 
 LOCAL_SOURCE = USART.c interrupts.c adc.c sensors.c integers.c lcdroutines.c \
-display.c
+display.c alert.c
 
 ## Here you can link to one more directory (and multiple .c files)
 EXTRA_SOURCE_DIR = 
diff --git a/lambda/alert.c b/lambda/alert.c
new file mode 100644
index 0000000..3388603
--- /dev/null
+++ b/lambda/alert.c
@@ -0,0 +1,49 @@
+/*
+ * alert.c
+ *
+ *  Created on: 24.04.2015
+ *      Author: dode@luniks.net
+ */
+
+#include <stdio.h>
+#include <stdbool.h>
+#include <avr/io.h>
+#include "USART.h"
+#include "alert.h"
+
+uint8_t oscCount = 0;
+uint8_t beepCount = 0;
+uint8_t beepLength = 0;
+
+void oscillate(void) {
+	if (beepCount == 0) {
+		return;
+	}
+	if (oscCount == 0) {
+		// turn beep on
+		DDRB |= (1 << PB1);
+	}
+	if (oscCount == beepLength) {
+		// turn beep off
+		DDRB &= ~(1 << PB1);
+		beepCount--;
+		if (beepCount == 0) {
+			// clear alert
+		}
+	}
+	oscCount == beepLength * 2 ? oscCount = 0 : oscCount++;
+}
+
+void beep(uint8_t beeps, uint8_t length) {
+	oscCount = 0;
+	beepCount = beeps;
+	beepLength = length;
+}
+
+void alert(uint8_t beeps, uint8_t length, char* line0, char* line1) {
+	oscCount = 0;
+	beepCount = beeps;
+	beepLength = length;
+	// set alert
+	// set display text
+}
diff --git a/lambda/alert.h b/lambda/alert.h
new file mode 100644
index 0000000..bfae948
--- /dev/null
+++ b/lambda/alert.h
@@ -0,0 +1,17 @@
+/*
+ * alert.h
+ *
+ *  Created on: 24.04.2015
+ *      Author: dode@luniks.net
+ */
+
+#ifndef ALERT_H_
+#define ALERT_H_
+
+void oscillate(void);
+
+void beep(uint8_t beeps, uint8_t length);
+
+void alert(uint8_t beeps, uint8_t length, char* line0, char* line1);
+
+#endif /* ALERT_H_ */
diff --git a/lambda/display.c b/lambda/display.c
index 6f4ff99..cdbfa3c 100644
--- a/lambda/display.c
+++ b/lambda/display.c
@@ -38,11 +38,11 @@
 void update(measurement meas) {
 	measMin.tempI = MIN(measMin.tempI, meas.tempI);
 	measMin.tempO = MIN(measMin.tempO, meas.tempO);
-	measMin.lambda = MIN(measMin.lambda, meas.lambda);
+	measMin.lambda = MAX(measMin.lambda, meas.lambda);
 
 	measMax.tempI = MAX(measMax.tempI, meas.tempI);
 	measMax.tempO = MAX(measMax.tempO, meas.tempO);
-	measMax.lambda = MAX(measMax.lambda, meas.lambda);
+	measMax.lambda = MIN(measMax.lambda, meas.lambda);
 
 	if (position == MENU_MIN_VALUES) {
 		display(measMin, "|<");
diff --git a/lambda/interrupts.c b/lambda/interrupts.c
index 8ad80d1..f2044d5 100644
--- a/lambda/interrupts.c
+++ b/lambda/interrupts.c
@@ -13,9 +13,6 @@
 	// pull-up resistor for the mouton
 	// INT0 and INT1 are assigned to the LCD, a bit of a shame
 	PORTB |= (1 << PB0);
-
-	// PB1 as output (just for testing)
-	DDRB |= (1 << PB1);
 }
 
 void setupSleepMode(void) {
@@ -26,10 +23,6 @@
 	// enable ADC interrupt
 	ADCSRA |= (1 << ADIE);
 
-	// enable PC interrupts
-	// PCICR |= (1 << PCIE0);
-	// PCMSK0 |= (1 << PB0);
-
 	// enable timer 0 overflow interrupt
 	TIMSK0 |= (1 << TOIE0);
 
@@ -39,6 +32,15 @@
 
 void initTimers(void) {
 	// timer in normal mode is default
-	// timer clock prescaler /64 = 15.625 kHz overflowing every 16.2 ms
-	TCCR0B |= (1 << CS00) | (1 << CS01);
+	// timer clock prescaler/64 = 15.625 kHz overflowing every 16 ms
+	TCCR0B |= (1 << CS01) | (1 << CS00);
+
+	// toggle pin PB1 on compare match
+	TCCR1A |= (1 << COM1A0);
+	// CTC mode, TOP OCR1A
+	TCCR1B |= (1 << WGM12);
+	// timer clock prescaler/8
+	TCCR1B |= (1 << CS11);
+	// toggles PB1 at 3.9 kHz generating a 1.95 kHz beep
+	OCR1A = 32;
 }
diff --git a/lambda/lambda.c b/lambda/lambda.c
index e81ec84..87258d6 100644
--- a/lambda/lambda.c
+++ b/lambda/lambda.c
@@ -29,19 +29,21 @@
 #include "sensors.h"
 #include "integers.h"
 #include "display.h"
+#include "alert.h"
 
 volatile bool buttonPressed = false;
 volatile uint8_t intCount = 0;
 
 /**
- * Called every 16.32 ms.
+ * Called every 16 ms.
  */
 ISR(TIMER0_OVF_vect) {
 	intCount++;
+	oscillate();
 	if (bit_is_clear(PINB, PB0) && ! buttonPressed) {
-		// PORTB ^= (1 << PB1);
-		cycle();
 		buttonPressed = true;
+		cycle();
+		beep(3, 3);
 	} else if (bit_is_set(PINB, PB0)) {
 		buttonPressed = false;
 	}
@@ -63,8 +65,9 @@
 	// main loop
 	while (1) {
 		measurement meas;
-		if (intCount >= 60) {
+		if (intCount >= 61) {
 			intCount = 0;
+			// causes a click in the beep, because of sleep mode?
 			meas = measure();
 			update(meas);
 			print(meas);