Epson Multi-mode Data Controller MFJ-1278B - Manual (Page 288)

MFJ-1278B MULTI-MODE OPERATIONAL COMMANDS
TXDIDDLE ON/OFF Mode: Packet Default: OFF
Parameters:
ON
The MFJ-1278B uses the efficent square wave TXDIDLE routine.
OFF
The MFJ-1278B uses flags during TXDELAY period.
TXDIDDLE determines whether or not the MFJ-1278B uses a highly efficient square wave
signal in place of flags during the transmitter delay (TXDELAY) period. When TXDIDDLE
is ON, you may select even smaller TXDELAY intervals because the square wave presents
four times as many transitions as TXDIDDLE OFF does for your connectees' receive
synchronization.
TXDIDDLE is defaulted to the OFF setting to reflect that the function is inactive. However,
there are a number of TNCs on the market which claim to be AX.25 compatible, but do not
recognize valid AX.25 packets preceded by the TXDIDDLE keyup technique. You may
recognize the need to set TXDIDDLE OFF, if it appears that the station you're working is
unable to successfully receive your packets despite your adequate signal.
This failure of some TNCs to receive TXDIDDLEd packets may be a result of some
software carrier-detect schemes. All TAPR and derivative TNCs utilizing hardware-
generated carrier-detect receive both TXDIDDLEd and non-TXDIDDLEd packets with
equal efficiency.
Note that when TXDIDDLE is OFF, TXDELAYC is irrelevant! Therefore, the actual
TXDELAY yielded when TXDIDDLE is OFF is equal to TXDELAY*100ms plus any
AXDELAY time.