H3 Set the hysteresis value for channel 3. sets the value and polarity by which the output value must change in order to assert or release the setpoint output.
Issuing the H3 command without any parameters will return the current value in the form H3:+00100. , signifying that the setpoint must hold it’s “ON” status until the source value drops below S3-100.
If H1 is set to a negative value, then this signifies that the source value must increase beyond S3+100, after which point the setpoint will release, and the relevant output channel will change to the “OFF” condition. This command therefore allows the setpoint to be inverted.

See also A0, A1, A2, A3, S0, S1, S2, S3, H0, H1, H2, P1, P2, P3.