The HV2405E integrated circuit is not very common these days. This circuit was found in the August 1998 issue of Electronics Now magazine. The current is a few tens of milliamps.
This circuit of a 1978 American publication monitors a telephone line by triggering a relay. The...
When S1 is in 1, the circuit operates with of half the total power applied to the load. When in...
This power supply also has a fine adjustment feature. The transformer is 16 + 16 V with 3 A and...