DLMS or Device Language Message Specification (originally Distribution Line Message Specification), is the suite of standards developed and maintained by the DLMS User Association and has been co-opted by the IEC TC13 WG14 into the IEC 62056 series of standards. COSEM or Companion Specification for Energy Metering, includes a set of specifications that defines the Transport and Application Layers of the DLMS protocol. The DLMS User Association defines the protocols into a set of three specification documents namely Green Book, Yellow Book and Blue Book.
The IEC TC13 WG 14 defines the DLMS specifications under the common heading: "Electricity metering - Data exchange for meter reading, tariff and load control."
The IEC TC13 WG 14 defines the DLMS specifications under the common heading: "Electricity metering - Data exchange for meter reading, tariff and load control."
- IEC 62056-21: Direct local data exchange (3d edition of IEC 61107) describes how to use COSEM over a local port (optical or current loop)
- IEC 62056-42: Physical layer services and procedures for connection-oriented asynchronous data exchange
- IEC 62056-46: Data link layer using HDLC protocol
- IEC 62056-47: COSEM transport layers for IPv4 networks
- IEC 62056-53: COSEM Application layer
- IEC 62056-61: Object identification system (OBIS)
- IEC 62056-62: Interface classes
