Basic call state model
# Basic call state model

In Intelligent Network and CAMEL switching, a BCSM is a Basic Call State Model.

## Types

* O-BCSM (Originating BCSM)
* T-BCSM (Terminating BCSM)

A fundamental concept for IN control is the basic call state model (BCSM). When a call is processed by an exchange, the call goes through a number of pre-defined phases. These phases of the call are described in the BCSM. The BCSM generally follows the ISUP signalling of a call

## State machine description

In the following IN BCSMs, bold Detection Points and Points In Call are also present in the CAMEL Ph1 subset.

TODO: Expand to Ph2,3,4

### O-BCSM

**Points in call**

* 1. O_Null & Authorize Origination Attempt
* 2. Collected_info (Merged with 1. in CAMEL Ph1)
* 3. Analyze_Info
* 4. Routing & Alerting (Merged with 3. in CAMEL Ph1)
* 5. O_Active
* 6. O_Exception

**Detection Points**

* 1 Origination_Attempt_Authorized
* 2 Collected_Info
* 3 Analyzed_Info (this is the only Statically armed DP, others are dynamically armed using "Request Report BCSM (RRBE)" message by the SCP)
* 4 Route_Select_Failure
* 5 O_Called_Party_Busy
* 6 O_No_Answer
* 7 O_Answer
* 8 O_Mid_Call
* 9 O_Disconnect
* 10 O_Abandon

### T-BCSM

**Points in call**

* 7. T_Null & Authorize Termination_Attempt
* 8. Select_Facility & Present_Call
* 9. T_Alerting (Merged with 8. in CAMEL Ph1)
* 10. T_Active
* 11. T_Exception

**Detection Points**

* 12 Termination_Attempt_Authorized
* 13 T_Called_Party_Busy
* 14 T_No_Answer
* 15 T_Answer
* 16 T_Mid_Call
* 17 T_Disconnect
* 18 T_Abandon

## Messages

* Initial Detection Point (IDP)
* RRBE (Request Report BCSM)
* Event Report BCSM (ERB)
* Connect (CON)
* Continue (CUE)
* Send Charging Information (SCI)
* ACH (Apply Charging)
* ACR (Apply Charging Report)
