Alarm circuit to detect inadmissible drop in input level to repeater - applies to repeater amplifier in CW communication system when output level is also low

摘要

The alarm circuit detects any inadmissible drop in the input level to a repeater amplifier in a CW communications system when the output level is also inadmissibly low. The alarm is given if either a lower or upper level is exceeded after the control process has ended and when the pilot signal at the amplifier output exhibits a lasting inadmissible deviation in level. A multiple voltage divider with two tappings is used to generate ref. voltages of different polarity. These two reference voltages are applied to the control input of a first operational amplifier and to the inverting input of a second operational amplifier. The remaining two inputs are connected together. The outputs are connected via load resistors to a third operational amplifier.