Specifications

Danish Interpretation Systems Technical Specifications
Printed in Denmark
47
5.3 The Heart Beat process
After the external controller has been registered in the CU, it becomes part of the heart beat process.
The heart beat process consists of a pair of control messages, a reply from the CU and a response from
the external control unit. Every 5 seconds, the CU sends a Heart Beat Request to the external control
unit, and by responding by a Heart Beat Reply, the external control unit indicates, that it is an active
controller.
If the CU does not receive reply to 3 consecutive Heart Beat Requests, it assumes, that the control unit
has lost control of the CU.
The following sequence shows the Heart Beat communication:
External
Control Unit
CU
Heart Beat Response
Heart Beat ResponseHeart Beat Response
Heart Beat Response
<START> 'j' <ID> <0> <Addr MSB> <Addr LSB>
<27> <4> <0> <0> <CRC> <STOP>
Heart Beat Request
Heart Beat RequestHeart Beat Request
Heart Beat Request
<START> 'c' <ID> <15> <173> <27> <2>
<3> <Error Information> <CRC> <STOP>
Every 5 seconds, the CU requests
the external control unit to give a
'Heart Beat'.
Figure 3 - Heart Beats
5.4 Retrieving the microphone system status
After completing registration, the system status must be aligned between the external control unit and
the CU. The status of the CU must be transferred to the external control unit.
The complete status of the microphone system can be retrieved from the CU in two sets of
information:
- Microphone control system status
- Microphone audio system status