# Signal values

The following table lists the valid signal values in ACU_ALERT_IN, ACU_ALERT_RQ, ACU_CALL_PROC_IN, ACU_CLEAR_IN, ACU_CLEAR_RQ, ACU_CONN_CO, and ACU_PROGRESS_IN messages.

These values are defined in isdnval.h.

Signal value | Description
--- | ---
ACUDIAL_ON | Dial tone on.
ACURING_BACK_ON | Ring back tone on.
ACUNET_CONGEST_ON | Network congestion tone on.
ACUBUSY_ON | Busy tone on.
ACUTONES_OFF | Tones off.
ACUALERTING_OFF | Alerting off.
ACUCREDIT_CARD_TONE_ON | Credit card tone on.
ACUOUT_OF_RANGE_TONE_ON | Out of range tone on.
ACUQUEUING_TONE_ON | Queuing tone on.
ACUAUDIBLE_TONE_ON | Audible tone on.
ACUVISUAL_ALERT_1_ON | Visual alert #1 on.
ACUVISUAL_ALERT_2_ON | Visual alert #2 on.
ACUSATCOM_CALL_NOTIFY | SATCOM call notify.