MT88E45 データシートの表示（PDF） - Mitel Networks

部品番号

コンポーネント説明

一致するリスト

MT88E45

4-Wire Calling Number Identification Circuit 2 (4-Wire CNIC2)

Mitel Networks 

Advance Information

MT88E45

2130 Hz and 2750 Hz

CAS/DT-AS Characteristics

Bellcorea

(Off-hook only)

ETSIb

(Off-hook)

BTc

(Off-hook = ‘Loop State’)

(On-hook = ‘Idle State’)

Frequency Tolerance

Signal Level (per tone)

Reject Level (per tone)

Maximum Twist (V2130Hz/V2750Hz)

Duration

+/-0.5%

-14 to -32 dBmd

-45 dBm

+/-6 dB

75 to 85 ms

+/-0.5%

-9.78 to -32.78 dBm

(-12 to -35 dBVe)

+/-6 dB

75 to 85 ms

Off-hook: +/-0.6%

On-hook: +/-1.1%

+0.22 to -37.78 dBm

(-2 to -40 dBV)

On-hook: -43.78 dBm

(-46 dBV)

+/-7 dB

Off-hook: 80 to 85 ms

On-hook: 88 to 110 ms

Reject Duration

Off-hook: <=70 ms

On-hook: <=20 ms

Signal to Noise Ratio

Speech

Speech

Off-hook: Speech

On-hook: >= 20 dB

(300-3400 Hz)

Hybrid Op-amp (GS2) Gain

Vdd = 5V +/- 10%

0 dB

0 dB

0 dB

Hybrid Op-amp (GS2) Gain

Vdd = 3V +/- 10%

-3.5 dB

-3.5dB

TBD

a. SR-TSV-002476, Issue 1 Dec 1992

b. ETS 300 778-2 Jan 98. The DT-AS plus FSK variant of ETSI on-hook signalling described in ETS 300 778-1 is not supported

because on-hook DT-AS uses the GS1 op-amp. With the GS1 gain in Table 4, the minimum DT-AS level will be below the

MT88E45’s minimum accept level.

c. SIN227 Issue 3 Nov 97, SIN242 Issue 2 Nov 96

d. dBm - Decibels above or below a reference power of 1 mW into 600 ohms. 0 dBm = 0.7746 Vrms.

e. dBV - Decibels above or below a reference voltage of 1 Vrms. 0 dBV = 1 Vrms

Table 3 - CAS/DT-AS Characteristics

signalling. (BT calls it Tone Alert Signal.) The CAS/

DT-AS characteristics are summarized in Table 3.

Table 3 shows the Hybrid op-amp gain for operation

at 3V and 5V nominal Vdd, with a ± 10% Vdd

variation. For 3V operation, the Hybrid op-amp gain

should be reduced from the 5V setting to maintain

the CAS reject level and to maintain the talkoff

immunity: the CAS threshold is directly proportional

to Vdd, when Vdd is reduced the threshold becomes

lower, hence lower level CAS are accepted. If the

gain is not reduced, the MT88E45 will be more

talkoff prone.

When CAS detection is selected, the dual purpose

output pin DR/STD is STD. STD goes low when CAS

has been detected, and returns high after CAS has

ended.

CAS Guard Time

The guard time circuit shown in Figure 5 implements

a timing algorithm which determines whether the

signal is a CAS. Proper selection of the guard time(s)

is key to good speech immunity. The first indication

that there might be a CAS is when EST goes high.

EST high indicates that both tones are present. EST

low indicates that one or both tones is not present.

STD low indicates that CAS has been detected.

When STD returns high it indicates that CAS has

ended.

The timing algorithm consists of 2 components: a

tone present guard time (tGP) and a tone absent

guard time (tGA). tGP sets the minimum accept

duration for CAS. That is, both tones must be

detected continuously for tGP for STD to go low to

indicate that CAS has been detected. For STD to

return high to indicate that CAS has ended, one or

both tones must have disappeared for tGA. The

purpose of tGA is to bridge over momentary EST

dropouts once EST has met the minimum tone

duration so as to decrease the likelihood of a long

talkoff being broken up into several talkoffs. Usually

tGA is set very short or removed altogether because

there is another way to deal with the problem (by

ignoring further detections for 2 seconds after every

detection).

7

Share Link: