diff --git a/plip_voice/main/CMakeLists.txt b/plip_voice/main/CMakeLists.txt
index 9c79a3e..20ed31c 100644
--- a/plip_voice/main/CMakeLists.txt
+++ b/plip_voice/main/CMakeLists.txt
@@ -7,6 +7,9 @@ idf_component_register(
         "cmd_exec.c"
         "hook_client.c"
         "phone.c"
+        "tones.c"
+        "dialer.c"
+        "conversation.c"
     INCLUDE_DIRS "."
     PRIV_REQUIRES
         driver
@@ -14,6 +17,7 @@ idf_component_register(
         esp_http_client
         esp_http_server
         esp_netif
+        esp_timer
         esp_wifi
         json
         nvs_flash
diff --git a/plip_voice/main/tones.c b/plip_voice/main/tones.c
new file mode 100644
index 0000000..80f0604
--- /dev/null
+++ b/plip_voice/main/tones.c
@@ -0,0 +1,125 @@
+/*
+ * tones.c — France Télécom telephone tones (dial / busy / ringback).
+ *
+ * Generates 440 Hz sinusoid with on/off cadence written directly to the
+ * I2S speaker handle (stereo — ES8388 requires L+R pairs).
+ *
+ * Cadences (all at 440 Hz):
+ *   DIAL     : continuous
+ *   BUSY     : 0.5 s on / 0.5 s off (1 s cycle)
+ *   RINGBACK : 1.5 s on / 3.5 s off (5 s cycle)
+ */
+
+#include "tones.h"
+#include "audio.h"
+
+#include "freertos/FreeRTOS.h"
+#include "freertos/task.h"
+#include "driver/i2s_std.h"
+#include "esp_log.h"
+
+#include <math.h>
+#include <string.h>
+#include <stdbool.h>
+
+#define TAG "tones"
+
+typedef enum { TONE_NONE, TONE_DIAL, TONE_BUSY, TONE_RINGBACK } tone_mode_t;
+
+static volatile tone_mode_t s_mode = TONE_NONE;
+static TaskHandle_t         s_task  = NULL;
+
+#define SR    16000   /* sample rate (must match audio_init) */
+#define FRAME 320     /* 20 ms @ 16 kHz */
+
+/*
+ * Fill `n` stereo frames (L=R = 440 Hz sine) into buf.
+ * buf must hold n * 2 int16_t (stereo interleaved).
+ * ph: running phase accumulator (mono sample index).
+ */
+static void fill_440_stereo(int16_t *buf, int n, int *ph)
+{
+    for (int i = 0; i < n; i++) {
+        int16_t v = (int16_t)(8000.0f * sinf(2.0f * (float)M_PI * 440.0f * (*ph) / SR));
+        buf[i * 2]     = v;  /* L */
+        buf[i * 2 + 1] = v;  /* R */
+        (*ph)++;
+    }
+}
+
+static void tone_task(void *a)
+{
+    (void)a;
+    /* Stereo buffer: FRAME mono samples × 2 channels × 2 bytes = FRAME*4 bytes */
+    int16_t buf[FRAME * 2];
+    int ph = 0;
+    int64_t t = 0;  /* ms elapsed in current tone state */
+
+    for (;;) {
+        tone_mode_t m = s_mode;
+        if (m == TONE_NONE) {
+            vTaskDelay(pdMS_TO_TICKS(20));
+            t = 0;
+            ph = 0;
+            continue;
+        }
+
+        bool on = true;
+        if (m == TONE_BUSY) {
+            on = (t % 1000) < 500;          /* 500ms on / 500ms off */
+        } else if (m == TONE_RINGBACK) {
+            on = (t % 5000) < 1500;         /* 1.5s on / 3.5s off */
+        }
+        /* TONE_DIAL: always on */
+
+        if (on) {
+            fill_440_stereo(buf, FRAME, &ph);
+        } else {
+            memset(buf, 0, sizeof(buf));
+            /* Keep phase accumulator advancing so pitch is smooth on resumption */
+            ph += FRAME;
+        }
+
+        size_t written = 0;
+        i2s_channel_write(audio_spk_handle(), buf, sizeof(buf), &written, pdMS_TO_TICKS(500));
+        t += 20;  /* each frame = 20 ms */
+    }
+}
+
+static void ensure_task(void)
+{
+    if (!s_task) {
+        xTaskCreate(tone_task, "tones", 3072, NULL, 5, &s_task);
+        ESP_LOGI(TAG, "tone_task created");
+    }
+}
+
+void tones_dialtone_start(void)
+{
+    ESP_LOGI(TAG, "dial tone start");
+    audio_pa_set(true);
+    ensure_task();
+    s_mode = TONE_DIAL;
+}
+
+void tones_busy_start(void)
+{
+    ESP_LOGI(TAG, "busy tone start");
+    audio_pa_set(true);
+    ensure_task();
+    s_mode = TONE_BUSY;
+}
+
+void tones_ringback_start(void)
+{
+    ESP_LOGI(TAG, "ringback tone start");
+    audio_pa_set(true);
+    ensure_task();
+    s_mode = TONE_RINGBACK;
+}
+
+void tones_stop(void)
+{
+    ESP_LOGI(TAG, "tones stop");
+    s_mode = TONE_NONE;
+}
diff --git a/plip_voice/main/tones.h b/plip_voice/main/tones.h
new file mode 100644
index 0000000..5444a97
--- /dev/null
+++ b/plip_voice/main/tones.h
@@ -0,0 +1,7 @@
+#pragma once
+#include "esp_err.h"
+
+void tones_dialtone_start(void);   /* 440 Hz continuous */
+void tones_busy_start(void);       /* 440 Hz 0.5s on/off */
+void tones_ringback_start(void);   /* 440 Hz 1.5s/3.5s */
+void tones_stop(void);