title: Modem manager and ttyACM in use
body: <p>I have a script that gets the signal strength from a external Ericsson F3507gw modem, which is connected in:</p>
  
  <pre><code>ttyACM0: mobile broadband data modem
  ttyACM1: mobile broadband modem
  ttyACM2: GPS port
  cdc-wdm0: Device management
  cdc-wdm1: USIM port
  </code></pre>
  
  <p><code>cu -l /dev/ttyACM2</code> works fine to send the AT commands. When I do not run Ubuntu's modem manager (mobile broadband is disabled) I can run my script without any problem. However, when Ubuntu is connected using the modem manager sometimes I get:</p>
  
  <p><code>cu -l /dev/ttyACM2</code></p>
  
  <p><code>cu: /dev/ttyACM2: Line in use</code></p>
  
  <p>I have not figured out when, but I would like to fix it. My user is in the dialup group so there are no permission problems. Any ideas how to run my script without killing the modem-manager?</p>
  
  <p>The script simply sends AT commands using <code>echo</code>.  </p>