This circuit was found in a documentation of the 80s, having didactic purpose. For R1 values between 10k to 1M can be used. Transistors are general purpose types.
In this circuit of a 1956 publication, the handset must be high-impedance magnetic and L1 has 200...
The two circuits we suggest are from the book Optoeletronics - Theory and Practice by Texas...
The base of this circuit consists of two operational amplifiers of the type LMI101A. The first...