E.F. Johnson Company 5300 Series Instructions d'exploitation télécharger pdf (Page 183)

ES Series Mobile Radio Operating Manual 9-3

Data Features

Frame Sync Seek Period - Selects the amount of time the radio listens for a frame sync

sequence before a packet is transmitted. Times are 0 to 5000 msec., in increments of 50

msec. The default is 750 msec.

Tx Short Random Range - Selects the maximum amount of time the radio waits to

transmit once the first qualified FS is received indicating the channel is clear. Times are

50 to 500 msec., in increments of 50 The default is 50 msec.

Tx Long Random Range - Selects the upper range of the random range. When the

radio detects a busy, the radio uses a random time within this range (Back off delay) to

determine when to retransmit the packet. Times are 50 to 5000 msec., in increments of

50 msec. The default is 2000 msec.

Tx Response Random Range - Selects amount of time radio waits before rechecking a

channel's status once a busy channel status symbol has been received. Only applies to

ACKs. Times are 50 to 1000 msec., in increments of 50. The default is 1000 msec.

9.2.2 Interface Connection

The radio connects from its MDP Interface to the RS232 COM port of the computer using

the P25 Mobile Data Peripheral (MDP) Interface cable.

9.2.3 Context Activation

For the radio to access data service on a trunking system, it must be a valid user on the

system and it must be affiliated to an RF site. Once this is accomplished, the radio must

request data services from the trunked system through the process of context activation; a

data registration of the radio with the system. Context activation is initiated from the radio.

In an EFJohnson Technologies mobile radio, context activation is automatically initiated

when the user selects a P25 trunking system with either data registration enabled or OTAR

enabled. During a context activation, the mobile radio attempts to access a packet data

channel (PDCH) at the site and send it its request for data services. If the context

activation is successful, the mobile radio will receive a response containing a IP address.

This IP address will be used by the mobile radio as a source IP address for all inbound data

messages sent, and is used by the host application as the destination IP address for all

outbound data messages.

If for some reason the context activation fails, the mobile radio will not be allowed to use

data services on the trunked system. If a PPP link is established between the portable

computer and mobile radio without the radio context activated, any data transmitted by the

computer to the radio is ignored.

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E.F. Johnson Company 5300 Series Instructions d'exploitation Page 183