Motorola G24 Manuale Utente

The transmitter (referring to the sender of a frame) examines the frame between the opening and 
closing flag sequences (including the address, control and FCS fields) and, following completion 
of the FCS calculation, does the following:

When encountering protected characters, complements the 6th bit of the octet (XOR with 
0x20).

Inserts a control escape octet immediately preceding the octet resulting from the above, prior 
to transmission.

The receiver (referring to the receiver of a frame) examines the frame between the two flag octets. 
Upon receipt of a control escape octet, and prior to FCS calculation, it does the following:

Discards the control escape octet.

Restores the octet that immediately follows by complementing its 6th bit (XOR with 0x20).

Valid channel indexes in MUX state are 0 to 4, where 0 is the index of the control channel and 1-4 
are indexes of the information channels (IDLC).

The following table describes the basic procedures (Open/Close/Err) performed when the G24 is 
in MUX state.

The G24 ignores unrecognized and invalid frames.

Upon receiving a SABMi frame (i = channel index), the G24 checks 
whether i is within the valid range and is not already established. It them 
tries to establish the new channel. 
If the G24 succeeds, it sends a UA frame. If it is not successful, it sends 
a DM frame.

Upon receiving a DISCi frame (i = channel index), the G24 checks 
whether i is within the valid range and represents an open channel. If so, 
the G24 attempts to close the channel. 
If the G24 is successful, it sends a UA frame. If it is not successful, it 
sends a DM frame.
Closing a channel hangs up any active CDSs. However, active voice 
calls are not hung up, even after the IDLC is closed.