Ramsey Electronics BS2C Manual de instrucciones descargar pdf (Pagina 6)

DCI2 • 6

familiar think about the output of U3, a 4 line signal that represents the DTMF

signal received and then the 16 different DTMF signals. You guessed it, U2

constantly looks at the 4 output lines from U3 and sets one of it’s 16 outputs to

a low level, whenever the data valid signal is activated from U3, based on

which DTMF signal was received. While this device is not as complex as U1

and U3 it is still important. This circuit functions all the time no matter how the

DCI2 has been configured. This means that you can always tell which DTMF

signal is received. One of the 16 output lines will be activated, set to a low

level, whenever a valid signal is received. The 4 data input lines are on pins

20, 21, 22 and 23 of U2 and the data valid signal, supplied thru Q7 to pin 19.

Q7 is necessary because the data valid signal is the opposite level of what U3

provides. It simply inverts the level so a the high level from U3 for data valid is

changed to a low for use by U2.

Other Information

When the micro-controller, U2, receives valid data from the user, it flashes

LED D4 (the activity indicator) and sends a feedback tone back over the

phone line to let you know the command was received. Components R19,

R21, Q6, C5, D10 and D11 work together with the micro-controller to generate

the tone pulse. The pulsed tone output from U1:pin 11 is amplified from 0 to 5

VDC up to 0 to 12 VDC to ensure that enough signal will couple through to the

phone line. Protection diodes D10 and D11 limit the incoming signal on the

phone line (between +12.7 and - 0.7 V) so that potentially damaging voltages

like the 90 Vp-p ‘Ring’ signal does not blow up Q6!

A detailed description of each of the configurations is provided later in this

manual

The Power Supply

So far we have covered most of the circuitry on the board with exception of

the power supply. VR1 and the surrounding parts C3, C4 and the polarity

protection diode D1 form a simple voltage regulator to supply a steady 5 VDC

to the ICs on the board. By using this scheme, we can operate the unit with a

single 12 VDC (positive tip on J5) source and have access to the multiple

voltages needed for the unit to operate.

1 2 3 4 5 6 7 8 9 10 11 ... 33 34

Sin comentarios

Ramsey Electronics BS2C Manual de instrucciones Pagina 6