In this case, operators may prefer (or be forced) to rely on existing (possibly upgraded) metallic test access unit (MTAU) equipment to obtain a first estimate of data rate capability to a customer.

• 此时，运营商可能宁愿（或者是被迫）通过已有的（可能是升级过的）铜线测试接入单元（MTAU）设备来得到用户数据速率能力的初次估计。