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參數資料
| 型號： | CH1804 |
| 英文描述： | Telecommunication IC |
| 中文描述： | 通信集成電路 |
| 文件頁數： | 1/4頁 |
| 文件大小： | 363K |
| 代理商： | CH1804 |
Cermetek Microelectronics, Inc.
Document No. 603-0155 Rev. H (8/98) 1
CH1804/A, CH1809/A
LINE DETECTOR MONITOR
C
microelectronics
INTRODUCTION
The CH1804/A and CH1809/A are line status detectors that
are used to detect/monitor a device off-hook condition, or
severed, or cut telephone lines on a telephone line shared
by multiple devices. The CH1804/A is a single line monitor,
while the CH1809/A is a dual line device and can monitor
two telephone lines. The CH1804/A is a low cost subset of
the CH1809/A in the same package. The devices are used
for Alarm Systems to detect a severed telephone line. In
this mode, voltage of less than 8VDC is detected when both
lines of telephone line are cut. Or used for collision avoid-
ance in systems where multiple telephone line access can
occur. In this mode the detector will detect any time the
telephone line voltage drops below 25VDC and can be used
for off-hook detect.
Since the detector accesses the public switched telephone
lines, it must be FCC Part 68 approved. This approval is
provided with conveyed registration. A sticker is supplied
for placement on the user equipment in compliance with
FCC Part 68 requirements. The device operates on a single
5-volt supply and provides a separate active high indication
when either of the two attached lines is cut. Single in-line
package is 1.0 long and 0.5 high, requiring minimal PCB
area.
OPERATION
Each device contains one or two separate independent line
detector circuits with separate Tip and Ring inputs and ac-
tive high outputs for each circuit. A common 5-volt supply
provides power to both. The output of each detector circuit
has 45K ohm pull up resistance to 5 volts and 2.2 mF ca-
pacitance to ground. This is provided to filter out zero cross-
ing pulses which can occur during ringing. This resident
source of output drive current might not be sufficient for
some applications. It is permissible to add a lower value
resistor in parallel between the output and 5 volts, if the zero
crossing pulses are not objectionable (this resistor should
not be less than 1K ohms). If more drive current is needed
while retaining zero crossing filtering, an external capacitor
must be added to keep the RC time constant, the same, or
higher.
Telephone lines may not be isolated from each other via a
common TIP line or a common RING line due to the DC
voltage supplied on the telephone system. In addition, the
ground of the telephone system may be common to the
ground of the system where the detector is installed at the
earth ground connection. If this occurs in an installation,
the CH1809/4 can only detect if TIP and RING are both cut.
However, the CH1809A/4 will always detect an off hook con-
dition. If it is desirable to detect a single line cut from either
leg or of a given telephone line, then the logical OR of volt-
age and not current is required. This can be done with the
CH1808 line status detector for a single line.
FEATURES
leased lines.
Detects a severed telephone cable. Does not require
polling.
Single in line package (SIP) requires minimum PCB
area.
Low power operation. SIngle 5V operation.
FCC Part 68 approved with conveyed registration
Usable on public switched telephone lines and wet
1804/A, 1809/A
Detects a Cut Line
On the Local Loop
Detects Devices Offhook
1804/1809 1804A/1809A
X
X
X
X
Figure 1. CH1804/A, CH1809/A Functional Block Diagram
When using each detector circuit, external leakage and capaci-
tance on each TIp and Ring input must be minimized. Differential
leakage to Tip and Ring in excess of 0.1 microamperes can ap-
pear like a central office battery voltage to the detector circuit. Com-
mon mode leakage to Tip andRing in excess of 1 microampere is
also undesirable. Thus the circuit board layout and external wiring
for Tip and Ring must be well insulated.
Capacitance on Tip and Ring should also be minimized as it could
retain charge after a transition and appear like a central office
battery voltage for many tens of seconds or more. The input im-
pedance of the detector circuit is approximately 10M ohms to
ground, and teh capacitance may have to be discharged for 3 or 4
time constants to indicate a detection depending on initial condi-
tions. Thus it would be desirable to keep capacitance well below
1
μ
F to keep the delay from exceeding tens of seconds.
If the detector is the only device on the telephone line, leakage and
differential capacitance will tend not to affect normal operation,
since the line capacitance in the central office or the local loop are
the only consideration. The more devices that share a given local
loop, such as modems and extension telephones, the greater the
capacitance and leakage possibilities. Sources of capacitance,
when on hook, include ring detection circuits in modems.
相關PDF資料 |
PDF描述 |
|---|---|
| CH1804A | Telecommunication IC |
| CH1807 | Telecommunication IC |
| CH1808 | Telephone Circuit (Support) |
| CH1809 | CUT LINE DETECTOR|SIP|10PIN|PLASTIC |
| CH1809A | LOOP TRANSCEIVER/DETECTOR|SIP|10PIN|PLASTIC |
相關代理商/技術參數 |
參數描述 |
|---|---|
| CH1804A | 制造商:未知廠家 制造商全稱:未知廠家 功能描述:Telecommunication IC |
| CH1807 | 制造商:未知廠家 制造商全稱:未知廠家 功能描述:Telecommunication IC |
| CH1808 | 制造商:未知廠家 制造商全稱:未知廠家 功能描述:Telephone Circuit (Support) |
| CH1809 | 制造商:未知廠家 制造商全稱:未知廠家 功能描述:CUT LINE DETECTOR|SIP|10PIN|PLASTIC |
| CH1809A | 制造商:未知廠家 制造商全稱:未知廠家 功能描述:LOOP TRANSCEIVER/DETECTOR|SIP|10PIN|PLASTIC |
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