We found this circuit in an old Mullard (Philips) documentation on the 555 and 556 integrated circuit (double 555). The relay must be 12 V with contacts that support the horn current.
This power source was found in an old Argentine publication from 1973. The transistor could be the...
With this circuit it is possible to monitor a signal that is being recorded on an old tape...
This circuit is from a 70s documentation. The maximum sampling rate is 800 Hz. The operational...