SONET OC-N channel. An ADM can be configured for either the add-drop or terminal mode. In the ADM mode, it can operate when the low-speed DS1 signals terminating at the SONET derive timing from the same or equivalent source as (SONET) (i.e., synchronous) but do not derive timing from asynchronous sources. Figure 19.14 is an example of an ADM configured in the add-drop mode with DS1 and OC-N interfaces. A SONET ADM interfaces with two full-duplex OC-N signals and ADVANCED BROADBAND DIGITAL TRANSPORT FORMATS Table 19.1 Line Rates for Standard SONET Interface Signals OC-N Level STS-N Electrical Level Line Rate (Mbps) STS-1 electrical 51.84 STS-3 electrical 155.52 OC-12 STS-12 electrical 622.08 OC-24 STS-24 electrical 1244.16 OC-48 STS-48 electrical 2488.32 OC-192 STS-192 electrical 9953.28 Common Optical equipment Network fiber termination management Alarms Technician interface terminations DSX and OC inputs/outputs Synchronization termination Optical fiber interface Timing references Notes: DSX = DS1-DS3 and OC (optical carrier, SONET) OA & M = Operations, administration and maintenance Figure 19.14 SONET ADM add-drop configuration example. one or more full-duplex DS1 signals. It may optionally provide low speed DS1C, DS2, DS3, or OC-M (M < N) interfaces. There are nonpath-terminating information payloads from each incoming OC-N signal, which are passed the SONET ADM and transmitted by the OC-N interface at the other side. Timing for transmitted OC-N is derived from either (a) an external synchronization source, (b) an incoming OC-N signal, (c) each incoming OC-N signal in each direction (called through-timing), or (d) its local clock depending on the network application. Each DS1 interface reads data from an incoming OC-N and inserts data into an outgoing OC-N bit stream as required. Figure 19.14 is an example of an ADM configured in the add-drop mode with DS1 and OC-N interfaces. A SONET ADM interfaces with two full-duplex OC-N signals and one or more full-duplex DS1 signals. It may optionally provide low-speed D