Modular, portable data processing terminal for use in a radio frequency communication network

A portable data collection terminal comprising:

• a first processing unit capable of operating per a first set of communication software routines;
• a selected one of a plurality of radio transceivers, each of the plurality having different operating characteristics;
• and
• a second processing unit capable of isolating the first processing unit from differences in the operating characteristics of the plurality of radio transceivers.

In an RF communications network having a communication channel, an access point and a portable data collection terminal, wherein the portable data collection terminal having a transceiver which may be selectively powered up or down to conserve energy, a method used by the portable data collection terminal for gaining access to the communication network, comprising the steps:

• (a) powering up the transceiver;
• (b) sensing the communication channel for a first pred termined time;
• (c) if during the sensing of the communication channel the channel remained clear, transmitting to the access point;
• and
• (d) if during the sensing of the communication channel the did not remain clear, waiting for a second predetermined time, and branching to step (b).

In an RF communications network having a communication channel, an access point and a portable data collection terminal, wherein the portable data collection terminal having a transceiver which may be selectively powered up or down to conserve energy, a method used by the portable data collection terminal for gaining access to the communication network, comprising the steps:

• (a) powering up the transceiver;
• (b) resetting a retry count;
• (c) sensing the communication channel for a first predetermined time;
• (c) if during the sensing of the communication channel the channel remained clear, transmitting to the access point, else, if the channel did not remain clear, incrementing a retry count;
• and
• (e) if the retry count is 1 ss than a threshold value, branching to step (c), else, powering down the transmitter for a period of time before branching back to step (a).

In a local area communications network having a communication channel, a host computer, an access point, and a portable data collection terminal, wherein the portable data collection terminal has the capability to enter a sleep mode when not transmitting or receiving, and the access point periodically transmit SYNC messages, a method used by the portable data collection terminal for gaining access to the communication network, comprising the steps:

• (a) waking up when data is available for transmission to the host computer;
• (b) waiting for a first predetermined time in order to receive a SYNC message from the access point;
• (c) sensing the communications channel for a second predetermined time to determine if the channel is busy;
• (d) transmitting a-request for poll to the access point if the channel is clear for the second predetermined time;
• and
• (e) if the channel is busy during the second predetermined time, repeating step (b).

In a communication network having a first and second subnetwork, a portable data collection terminal comprising:

• a base processing unit capable of operating per a first set of communication software routines;
• a first selected one of a plurality of radio transceivers, each having different operating characteristics;
• a second selected one of a plurality of radio transceivers, each having different operating characteristics;
• and
• a communication process capable of isolating the base processing unit from differences in the operating characteristics of the first and second radio transceiver.