application note CMX673 suggested applications 1998 mx com, inc. www. mxcom.com tel: 800 638 5577 336 744 5050 fax: 336 744 5054 doc. # 20830117.002 4800 bethania station road, winston-salem, nc 27105-1201 usa. all trademarks and service marks are held by their respective c ompanies. the CMX673 is a signal detector that operates on energy in the frequency band of about 300 to 650hz. its primary use is in the detection of status tones encountered in a telephone system. these tones include dial tone, circuits busy, ring tone, station busy, and others. identification of specific status tones is derived by examining the specific on/off cadence of the CMX673s tone detector output. featuring both high accuracy and rapid response time makes the CMX673 well suited for the rapid/short cadences used for services such as voice message waiting indication (vmwi). this application note shows some typical applications (figures 1, 2, 3, and 4), a simple scheme for connecting the CMX673 to a balanced telephone line (figure 5), and some common call progress tone cadences and frequencies (tables 1 and 2) and an illustrative cadence timing diagram (figure 6). off/on hook control telephone / adjunct box (cpe) with flashing voice message waiting indicator CMX673 stutter dialtone type vmwi central office c cmx602a fsk type vmwi led line interface phone line using the output signals of the CMX673 and cmx602a, the c identifies both the stutter dial tone and fsk types of voice message waiting indication signals that are popular in the u.s. the central office generates the stutter dial tone for a short period each time the cpe is taken off hook. if voice messages are waiting, the c flashes the led to notify users without the user having to operate the phone or lift its handset. figure 1: low cost dual type u.s. voice message waiting indication phone line rx- tx+ txd rxd cmx624/ cmx644 microcomputer modem ic dtmf dialer ic CMX673 2to 4 wire figure 2: detecting dial tone and secondary dial tones in an automatic dialing data modem
suggested applications for the CMX673 2 application note 1998 mx com, inc. www. mxcom.com tel: 800 638 5577 336 744 5050 fax: 336 744 5054 doc. # 20830062.002 4800 bethania station road, winston-salem, nc 27105-1201 usa. all trademarks and service marks are held by their respective c ompanies. central office digit receiver CMX673 computer figure 3: call detail and completion monitor in a billing system calling station digit receiver dialer ic CMX673 loop control central office cmx605 or cmx615 call progress generation power microcomputer figure 4: call routing in a speed dialing system ~ +5 10w 5% mlc 1f gnd 20% r3 49.9k r4 54.9k rf 499k 8 7 6 vdd vref vss microcomputer 4 port 1 port 2 detect enable xout xin sigin 3.58 mhz 5 3 2 1 - + 499k 499k 0.001f 300v 0.001f a b phone line resistors = 1% capacitors = 1 to 2 % except where noted figure 5: monitoring signals from a balanced phone line
suggested applications for the CMX673 3 application note 1998 mx com, inc. www. mxcom.com tel: 800 638 5577 336 744 5050 fax: 336 744 5054 doc. # 20830062.002 4800 bethania station road, winston-salem, nc 27105-1201 usa. all trademarks and service marks are held by their respective c ompanies. sig.in enable detect abccc t l t gd t rp t drp t rp t i key a = signal within call progress detection range, but not of sufficient duration to be detected b = continuous call progress tone. i.e. dial tone c = 3 bursts of 0.1seconds followed by a continuous tone (not shown) in the call progress band. i.e. recall dial 1 t i = burst length ignored t l = burst length detected t gd = call progress tone gap length detected t rp = call progress response time t drp = call progress tone de-response time figure 6: an example of tone detection (via tone cadence) using the CMX673 the minimum level required by the CMX673 is -38dbm. in general, to optimize transient response and to limit spurious detects, it is best to use the least sensitive configuration possible. the gain of the buffer stage shown in figure 4 is equal to the ratio of rf to rin and may be varied to obtain the sensitivity required for a given application. balanced network input impedance provides rejection of common mode signals. if component values are changed to obtain different gain, then the parallel combination of rf and r4 must be kept equal to r3 to maintain proper balance. closely matching 1% resistor and capacitor values should also be used. stutter dial tone cadence 10 bursts (each 0.1 sec on / 0.1 sec off) then steady on. frequencies 350 + 440 hz dial tone cadence on, steady frequencies 400, 425, 350 + 440, 600 x 120, 33 hz audible ring cadence 2 sec. on, 4 sec. off or 1/3 sec. on, 1/3 sec. off, 1/3 sec. on, 2 sec off frequencies 400, 425, 440 + 480, 420 x 40, 450 ,400 x 25 hz line busy cadence 0.5 sec. on, 0.5 sec. off, , frequencies 400, 425, 480 + 620, 600 x 120, 450 hz recorder (busy circuits) cadence 0.25 sec. on, 0.25 sec. off, or 0.5 sec. on, 1 sec off, frequencies 400, 425, 480 + 620, 600 x 120, 450 hz table 1: some common call progress tone cadences and frequencies
suggested applications for the CMX673 4 application note 1998 mx com, inc. www. mxcom.com tel: 800 638 5577 336 744 5050 fax: 336 744 5054 doc. # 20830062.002 4800 bethania station road, winston-salem, nc 27105-1201 usa. all trademarks and service marks are held by their respective c ompanies. cadence continuous tone continuous tone 3 burst of 0.1 seconds followed by a continuous tone (e) 3 burst of 0.1 seconds followed by a continuous tone (e) burst 0.5 seconds / silence 0.5 seconds burst 0.5 seconds / silence 0.5 seconds burst 0.25 seconds / silence 0.25 seconds burst 0.25 seconds / silence 0.25 seconds burst 2 seconds / silence 4 seconds burst 1 seconds / silence 3 seconds burst of 0.3 seconds every 10 seconds station call waiting : burst of 0.3 seconds outside call waiting: 2 bursts of 0.1 seconds (e) urgent call waiting: 3 bursts of 0.1 seconds (e) a 2.0 second burst followed by o.5 second bursts every 10 seconds bursts of 1.5 to 2.0 seconds followed by (f) burst of 3.0 seconds burst of 0.1 seconds / silence 0.1 second / burst 0.3 seconds 3 bursts 0.1 seconds (e) power per frequency at exchange(b) where tone is applied (c) -13dbmo -16dbmo -13dbmo -16dbmo -24dbmo -21dbmo -24dbmo -21dbmo -19dbmo -16dbmo -13dbmo -16dbmo -16dbmo -16dbmo -13dbmo -14dbmo -14dbmo -13dbmo -16dbmo 620 x x x x 480 x x x x x x 440 x x x x x x x x x x x x x 350 x x x x x x tones dial tone dial tone C modern pabx only recall dial tone recall dial tone C modern pabx only (g) busy tone busy tone C modern pabx only reorder tone reorder tone C modern pabx only audible ringing tone audible ringing tone C modern pabx only call waiting tone call waiting tone C modern pabx only (g) busy verification busy verification C modern pabx only (g) executive override C modern pabx only (g) confirmation tone confirmation tone C modern pabx only (g) (a) frequency limits are 0.5% of the niominal frequency. (b) pabx tone levels are measured at the pabx interfaces (typically at customer premises). power levels are 2db lower for priv ate line interfaces. (c) power level tone tolerances are +1.5db (d) tolerance level for pabx dial tone is +0.75db. (e) bursts are separated by 0.1 seconds (f) burst of 1.5 to 2.0 seconds before attendant intervenes, followed by repeated bursts of 0.5 to 0.8 seconds, 8 to 20 seconds apart (g) tones applied at pabx station or private line interfaces and not at the exchange interfaces. t able 2: call progress tone cadence and frequencies - taken from the ccitt blue book (fascicle ii.2 - suppl. no. 3)
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