This section of IEC 835-2 deals with the measurement of terminal-to-terminal protection switching equipment associated with digital radio-relay systems. The measurement methods described in this section of IEC 835-2 for an N+1 switching configuration but are also applicable to N+2 switching arrangements. The same measurement methods are applicable to 1+1, twin-path and hot standby arrangements. The channel priority status tests described in clause 5 are only applicable to the N+1 and N+2 switching arrangements. In configurations where the protection switching equipment is physically separable from the radio terminal equipment (see figure 1), the inte rfaces at the input and output ports of the switching equipment shall be measured in accordance with IEC 835-2-5.