Channel clarification
This was unclear from the docs.
//! It can be used concurrently by multiple producers (senders) and multiple
//! consumers (receivers), i.e. it is an "MPMC channel".
//!
+//! Receivers are competing for messages. So a message that is received by
+//! one receiver is not received by any other.
+//!
//! This queue takes a Mutex type so that various
//! targets can be attained. For example, a ThreadModeMutex can be used
//! for single-core Cortex-M targets where messages are only passed
