Digital Line to POTS Interface

CMX615

© 1999 Consumer Microcircuits Limited

17

D/615/4

CCITT ‘R1’ Signalling Tones

Field 2

(Hz)

(Hex)

700+900

$12

700+1100

$13

900+1100

$23

700+1300

$14

900+1300

$24

1100+1300

$34

700+1500

$15

900+1500

$25

1100+1500

$35

1300+1500

$45

700+1700

$16

900+1700

$26

1100+1700

$36

1300+1700

$46

1500+1700

$56

CCITT ‘R2’ Signalling Tones

Forward mode

Backward mode

Field 3

Field 3

(Hz)

(Hex)

(Hz)

(Hex)

Off

$00

Off

$00

1380+1500

$89

1140+1020

$65

1380+1620

$8A

1140+900

$64

1500+1620

$9A

1020+900

$54

1380+1740

$8B

1140+780

$63

1500+1740

$9B

1020+780

$53

1620+1740

$AB

900+780

$43

1380+1860

$8C

1140+660

$62

1500+1860

$9C

1020+660

$52

1620+1860

$AC

900+660

$42

1740+1860

$BC

780+660

$32

1380+1980

$8D

1140+540

$61

1500+1980

$9D

1020+540

$51

1620+1980

$AD

900+540

$41

1740+1980

$BD

780+540

$31

1860+1980

$CD

660+540

$21

1.6.2

‘C-BUS Timing

The relationship between bytes loaded onto the C-BUS and the transmission of FSK bytes is shown

diagrammatically in Figures 7a, 7b and 7c.

There are many ways in which the C-BUS can be used to program a device and three suggestions

(one for asynchronous FSK - Figure 7a - and two for synchronous FSK -Figures 7b and 7c) are shown

here, together with typical timings. Please note that the C-BUS timing is not shown to the same scale

as the FSK output (it has been magnified by at least 20 times to make it visible on the same scale).