We have a Pager that works, but no pager service is available. People have moved on to phones.
Amateur radio receivers
Features
- Incoming SMS
- Outgoing Landline
Quad Differential Comparator LM339
These devices consist of four independent voltage comparators that are designed to operate from a single power supply over a wide range of voltages. Operation from dual supplies also is possible, as long as the difference between the two supplies is 2 V to 36 V, and VCC is at least 1.5 V more positive than the input common-mode voltage. Quad Comparator LM339
An application from an old TI datasheet showing the versatility of this comparator. For me it was a workhorse and like LM324 was used in many products.
Current drain is independent of the supply voltage. The outputs can be connected to other open-collector outputs to achieve wired-AND relationships.
Differential to TTL convertor using LM339
- Single Supply or Dual Supplies
- Wide Range of Supply Voltage:
- Low Supply-Current Drain Independent of Supply Voltage… 0.8 mA Typ
- Low Input Bias Current …25 nA Typ
- Low Input Offset Voltage . . . 2 mV Typ
- Common-Mode Input Voltage Range Includes Ground
- Differential Input Voltage Range Equal to Maximum-Rated Supply Voltage . . . ±36 V
- Low Output Saturation Voltage
- Output Compatible With TTL, MOS, and CMOS
