the Data Store rack, one at the position representing the directory number and another at the position representing the equipment number. This can be seen in the photograph together with some plastic strips hanging by wire. Hanging the strips by wire was a common practice for subscribers who were constantly changing their Class of Service, i.e. being made TOS. This information was then pulsed by the common control translator and appropriate action taken. In the end the problem turned out to be cable interference requiring substantial re-cabling at the rear of the rack. This system was replaced in later TXE exchanges by Dimond rings. 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. The MF senders/receivers were used when an MF subscriber initiated a call. They were set up to the subscribers line and switching network to an MF register, they converted the MF tones to pulses for the registers to store. They used the X, Y and auxiliary switching planes. Incoming registers used a time-shared electronic dial path (TDM) to transfer pulsing information from the incoming junction to the incoming register. This feature was necessary to ensure that no pulsing information was lost. In the event of a cable breakdown or similar event which may result in permanent loops on subscribers lines, after a predetermined time the register would be forcibly released