 Until sufficient digits have been received to determine the outgoing route from the exchange, the instruction will be "apply again after the next digit" and the MCU returned to serving other demands.When sufficient digits had been received, the MCU would have been able to determine the required path through the exchange, the routing digits to be sent (if an outgoing call is indicated), and which of the received digits have to be repeated forward.It would advise the register accordingly and then set the paths necessary to allow the register to signal forward and finally extend the caller to the required number or junction.