The registers looked after all the dialling, and there were three sorts of registers: loop-disconnect, MF (later called DTMF), and incoming. There were about 20 local registers and 12 incoming registers. The local registers (loop-disconnect and MF) took care of own-exchange and outgoing calls, while the incoming registers dealt with calls coming into the exchange. A local register would provide dial tone to the subscriber, wait for the first dialled digit, and then apply to the translator to see what action was required. The translator could decide by the first digit if it was a local call, and if it was it would instruct the register to come back when it had all the digits. If it was not a local call and therefore to be routed out of the exchange, then it would tell the register to come back with each digit until it could decide on the routing, as not all calls went to the GSC (Group Switching Centre) as there was AAR (alternative available routing). Once the routing had been decided and digits passed on, the register was free to take another call.