The herpstat 2 and the Herpstat 4 are literally 2 and 4 thermostats crammed into 1 box respectively. In the case of multi channel thermostats the heat sources don't need to be identical.
A better way to look at this is to say 1 probe = 1 heat source.
The The herpstat intro, the herpstat intro +, the Herpstat 1 basic, and the herpstat 1 only have 1 probe
The herpstat 2 has 2 probes, and the herpstat 4 has 4 probes.
herpstat 1:
Herpstat 2:
herpstat 4:
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