An analog RSP signal can be used to adjust the value of the effective setpoint, as an alternative to using manually entered local setpoints.
A controller with remote setpoint has a 2nd auxiliary input that can accept a mA or VDC signal (or in some cases potentiometer or mV signal) which can be scaled and used as the setpoint source.
The remote setpoint value is constrained by the input range and any setpoint limits.
Typical uses for remote setpoint inputs are multi-zone setpoint and master & slave applications and on cascade control slaves.