# Maintenance mode - ProSBC and TMG
## Graceful Shutdown for new incoming calls
This guide outlines the procedure for isolating a Telcobridges TMG or ProSBC systems to perform bleed off active calls for maintenance period.
This method allows existing calls to finish naturally while elegantly rejecting all new incoming calls with specific cause codes.
***
### 🛠 Prerequisites
* Access to the Web User Interface.
* Permissions to edit and activate Routing Scripts.
* A defined configuration for testing. Our example: (e.g., `MSGC_TG_V11_DaveTest`).
***
### 📝 Step 1: Modify the Routing Script
To stop new calls from being processed, you must add a before filter to your main simple\_routing script.rb file.
1. Navigate and click >> **Routing Scripts** left-hand side of the menu.
2. Click on `simple_routing.rb`.
3. Locate the `class SimpleRouting < BaseRouting` definition line within the script.
4. Add the following line as a `before_filter`: right below last Include line.
```ruby
before_filter :proc => proc { |p| raise RoutingException, :no_circuit_available }
```
5. Scroll down to the bottom of the simple\_routing.rb script page and save.
6. Validate the configuration change. Activate the configuration change.
Note: Activation of new configuration will NOT terminate active calls.
7. Monitor Call Trace Page
8\. Monitor Call Status Page
Quick Notes:
Insert a # character in front the before\_filter to deactivate the call rejection progress.
```
## before_filter :proc => proc { |p| raise RoutingException, :no_circuit_available }
```
You can also modify your cause code to your preference. no\_circuit\_available
```
before_filter :proc => proc { |p| raise RoutingException, :no_circuit_available }
```
Reaon Cause Mapping definitions can be found in Web UI >> Profiles >> "Selected Profile" >> Edit Reason Cause Mapping
Activate Call rejection. before\_script is working...
Deactivate Call rejection. before\_script is not-working...
Repeat Step 5 and 6. Save Script. Validate and Activate new configuration.
