Codan Radio P25 Training Guide - Manual (Page 78)

TRAINING GUIDE | P25 RADIO SYSTEMS
Chapter 5: Conventional Fixed Station Interface Page 70
Control Service
The Control Service provides control capabilities similar to the control capabilities of the analog fi xed
station interface. The Control Service also establishes and maintains the connection between the host
and fi xed station.
There are ten control messages defi ned for the DFSI as shown in Table 5-2.
Message Name Description
FSC_CONNECT Sent by the host only to establish a connection with the fi xed station.
FSC_HEARTBEAT Sent periodically by both the fi xed station and the host to establish
and maintain heartbeat connectivity.
FSC_ACK Sent by both the host and the fi xed station to acknowledge (or not
acknowledge) the receipt of a control message.
FSC_SBC Sent by both the host and the fi xed station to convey Single Block
Control messages such as Emergency Alarm and Telephone
Interconnect Dialing.
FSC_MAN_EXT Sent by the host and the fi xed station to convey manufacturer
specifi c value added control messages.
FSC_SEL_CHAN Sent by the host to select the fi xed station receive and transmit
channels.
FSC_SEL_RPT Sent by the host to select repeat or non-repeat mode of the fi xed
station.
FSC_SEL_SQUELCH Sent by the host to select the squelch mode (monitor) of the fi xed
station.
FSC_REPORT_SEL Sent by the host to cause the fi xed station to report selected modes
(repeat, squelch, channel select) back to the host.
FSC_DISCONNECT Sent by the host to disconnect from the fi xed station.
Table 5-2: Control Service Messages
Voice Conveyance Service
The Voice Conveyance Service passes RTP payloads between the host and the fi xed station. The
Voice Conveyance Service will transport information to and from both an analog and a digital fi xed
station. The RTP payload for a digital transmission carries the entire Common Air Interface voice
frames including voice encoded with IMBE (and potentially encrypted), Link Control Word, Encryption
Synch Word, and Low Speed Data. The RTP payload for an analog transmission carries μ law PCM
audio, that includes all voice information and possibly in-band signaling.
The Voice Conveyance Service transports full-duplex clear (non-encrypted) or secure (encrypted)
audio, PTT and COR signaling (by way of start of stream information), voter identifi cation and CAI
information such as Unit ID (or Console ID), TGID, NAC, and Emergency bit between the fi xed station
and its host.