At the very least:-
Armed_status: ;PinC.1
SerTxd("Armed Status is Disarmed - sound 0004", CR, LF)
SetFreq BAUD_FREQ
Pause 10
SerOut TX, BAUD, ( $7E, $FF, $06, $0F, $00, $01, $04, $EF )
SerTxd(" ", CR, LF)
gosub Check_Busy
SetFreq MDEFAULT
toggle Armed_state
goto Begin ;***...