Larger 5XB systems were built in the 1960s with more markers. To save money the markers were separated into two kinds: simple dial tone markers (DTM) just to connect the line to the OR, and completing markers (CM), many times more complex and expensive, to complete the call to or from a trunk. CM has, among other features, the ability to translate the first 3 digits of a phone number (or 6 when using a separate foreign area translator) to identify the correct outgoing trunks and handling.