P3181

ETALDOC 567/13

Page 3 of 5

October 2007

MATCHING RECOMMENDATIONS

Note - Fig. 2:

Typical distortion: excite from line at 150Hz to yield -10dBm @ 150Hz at line terminals.

Typical THD at line terminals will then be -90dBm (i.e. -80dBc).

For signals received from the line, the signal level present between terminals 1 and 3 of the transformer will be

approximately 6dB below the signal sustained at the line terminals.

Note - Figs. 2 and 3:

As line side components (22

μF, 27nF) are common to both 600Ω and complex matches, switching between

matches can be performed solely on equipment side.

When driven from a balanced (differential) TX drive with unbalanced (single-ended) high impedance recever,

the following modifications can assist in giving good transhybrid loss (typically better than 18 dB across

voiceband):

* If components on line side to be unchanged for 600

Ω/CTR21, compromise on 22nF.

† 4.7nF can also be fitted on 600

Ω circuit with only minor degradation.

Note - Figs. 2, 3, 4 and 5:

As P3181 transformer has a non-unity turns ratio, orientation in circuit should be observed

Patented

Fig. 2

Recommended Circuit

Recommended Circuit

LIN E

TX

600

27nF

22µF

1.0:1.1

P3181

EUROPEAN CTR21 COMPLEX MATCH

600

MATCH AND DISTORTION TEST CIRCUIT

Ω

360

27nF

Fig. 3

LIN E

TX

270

27nF

1.0:1.1

P3181

1k

82nF

750

150nF

22µF

4

3

61

43

6

1

27nF

*

15nF*

4.7nF

†

LIN E

LIN E

270

600

750

150nF

1k

390

82nF

15nF

Fig. 5

Fig. 4

RX A

RX A

TX A2

TX A2

TX A1

TX A1

2.2k

2.2k

10k

10k

22µF

22µF

P3181

P3181

600

Ω

CTR21

61

4

3

61

43

1.0:1.1

1.0:1.1