Monroe Electronics 935A - Manual (Page 6)

6
THEORY OF OPERATION
General:
The Model 935A Dual Tone Sender contains a Model 3223B Encoder
Controller and a Model 3171B Dual Tone Encoder both powered by
the wall mount power supply provided with the instrument.
A block diagram of the 935A is provided in Figure 2 on page 9.
Theory Of Operation:
A contact closure at one of the four pushbutton switches on the 935A
causes the Model 3223B-2 Encoder Controller to provide the
programmable memory in the Model 3171B with a binary input
sequence. Any one of the four sequences is selected upon the
pressing of the specific push button.
Upon receiving the proper BCD input sequence, the memory supplies
the digital tone generator in the 3171B with a logic low for a row and a
column for each of the four digits in the programmed sequence.
The output of the digital tone generator, a series of four dual tone
digits, is amplified and connected to the 935A output terminals through
the output transformer.