Honeywell t841a Installation Instructions Manual page 10

T841A HEATING-COOLING THERMOSTATS
L1 L2
Fig. 14. T841A with two auxiliary heat stages and AUX.HT. and EM.HT. LEDs. Provides auto fan in emergency heat.
Fig. 15. T841A with EM. HT. and AUX. HEAT LEDs. Provides outdoor reset when used with C815 Thermistor.
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