This circuit is from a 1980's documentation for telecommunications. The circuit is used in SSB and the diodes must be suitable types for the application. The audio input is low impedance.
This flasher with a well-known configuration was suggested by a 1977 publication by Radio Shack. The...
In the figure we have a practical idea for using the good junction of a partially burned...
The CMOS TLC555 [equivalent to the bipolar 555] can be used as a monostable in the configuration...