CH1804/A and CH1809/A
Family of Line Detection and Monitoring Products
INTRODUCTION
Off-Hook Detection. The CH1804A and CH1809A
The CH1804/A and CH1809/A are line status
detector circuits will indicate an Off-Hook condition
detectors that are used to monitor line off-hook status
when the voltage between the TIP and RING drops
for shared lines, or to detect a severed or cut
below 20.0VDC. The Off-Hook condition is indicated
telephone line. The CH1804/A is a single line monitor.
by the CH1804A (CH1809A) when the output of OUT1
The CH1809/A is a dual line device allowing two
(OUT2) is > 3.5V.
telephone lines to be monitored simultaneously and
contains two CH1804/A circuits (See Figure1). For
Cut Line Detection. The CH1804 and CH1809
ease of convertibility, both devices share the same pin
detector circuits will indicate a Cut Line condition when
out configuration.
the voltage between TIP and RING drops below
2.6VDC. The Cut Line condition is indicated by the
The primary application for CH1804 and CH1809
CH1804A (CH1809A) when the output of OUT1
products are security systems where detection of
(OUT2) is > 3.5V.
severed telephone lines is required. In this mode, a
voltage of less than 2.6VDC is detected as a cut line.
An alternate application is collision avoidance in
FEATURES
systems where multiple access to a shared line is
allowed. In this mode, the CH1804A and CH1809A
will indicate when the telephone line voltage drops
leased lines.
below 20VDC thereby detecting an off-hook condition.
Does not
require polling.
Since the CH1804A/9A products access the PSTN
system, FCC Part 68 approved is required. Cermetek
area.
provides this approval via conveyed registration. A
registration label is supplied for placement on the host
equipment
in
compliance
with
FCC
Part
68
requirements. The CH1804/A and CH1809/A devices
Table 1. Features Available By Product.
operate on a single 5-volt supply and provide a
Detection
Number of Lines
separate active high indication when either of the two
Feature
CH1804
CH1809
CH1804A
CH1809A
attached lines is cut. The product is contained in a
Cut Line
1
2
single in-line package 1.0” long and 0.5” high,
Off-Hook
1
2
requiring minimal PCB area.
OPERATION
General. Each device contains either one or two
CH1804/A independent line detector circuits.
Each
circuit contains separate TIP and RING inputs and
separate active high outputs. A common 5-volt supply
provides power. The output of each detector circuit
has a 45K ohm pull up resistance to 5 volts and a
2.2 µ F capacitance to ground. This is provided to filter
out zero crossing pulses which can occur during
ringing. Refer to Figure 1.
Figure 1. CH1804/A, CH1809/A Functional Block
Diagram
If the output drive current of the CH1804A/9A is not
sufficient, it is permissible to add a lower value resistor
(this resistor should not be less than 1K ohms)
ISOLATION REQUIREMENTS
between the output and 5 volts. However, this will
For maximum detection flexibility, incoming telephone
allow zero crossing pulses to occur.
If more drive
lines should not share a common TIP or RING line. In
current is needed while retaining zero crossing
addition, the ground of the PSTN system should not be
filtering, an external capacitor must be added to
common to the ground of the system where the
preserve the original RC time constant. See Figure 2.
CH1804A/9A is installed. If either of these conditions
2003 Cermetek Microelectronics, Inc.
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Document No. 607-0015 Revision C (05/03)
Cermetek Microelectronics, Inc.
CH1804/A and CH1809/A
occur in an installation, the CH1804/9 will only detect
Potential False Indication. The CH1804/A and
when TIP and RING are both cut.
However,
CH1809/A products reside on the telephone line and,
regardless
of
the
installation
wiring,
the
as such, are subject to transients produced by
CH1804A/CH1809A products will always detect an off-
electrical discharge and ring voltage transitions.
hook condition. If it is required to detect and identify
These may cause momentary false Cut Line or Off-
which line (i.e., either TIP or RING) has been cut, then
Hook indications.
The use of additional external
a voltage sense device is required, such as the
capacitance on the output may be required to reduce
Cermetek CH1808 line status detector product.
these false indications. The capacitance value to add
to each output should be determined by appropriate
analysis and testing for the particular application.
APPLICATION RECOMENDATIONS
Cermetek recommends that the outputs be level
Failure to Detect Cut Line. When using either the
detected as opposed to edge detected to minimize
CH1804 or the CH1809 products, external leakage
false indications on excessively noisy lines. Referring
and capacitance on TIP and RING must be minimized.
to Figure 2, typical values are 0.1 µ f and 30K ohms for
Differential leakage to TIP and RING in excess of 0.1
CX and RX, respectively.
microamperes may appear as a central office battery
voltage thereby causing the CH1804/9 to fail to detect
a cut line. Additionally, Common mode leakage to TIP
SUPPLEMENTAL PROTECTION
and RING in excess of 1 microampere is also
If the CH1804A/9A products are being used on
undesirable.
Thus, the circuit board layout and
telephone lines that are prone to high voltage
external wiring for TIP and RING must be well
transients, an FCC Part 15 A/B suppressor may be
insulated.
required. This consists of 1.25 A fuses in both TIP and
RING lines and a 350V voltage suppressor between
Off-Hook Indication Delay. Capacitance on TIP and
TIP and RING for transient protection. A ferrite bead
RING should be minimized as it could retain charge
inductor and 0.1 µ F capacitor (1500V) to ground may
after a transition and appear as a central office battery
also be required for EMI/RFI suppression.
See
voltage.
This will delay detection of an Off-Hook
Cermetek Application Note # 126. If the CH1804A/9A
condition for many tens of seconds.
The input
is being used with another Cermetek device where the
impedance of the detector circuit is approximately 10M
supplemental protection is already planned for or
ohms to ground, and the capacitance may have to be
available, the CH1804A/9A can share the protection if
discharged for 3 or 4 time constants to indicate a
a parallel connection to the TIP and RING pins is
detection depending on initial conditions.
Thus, it
made in front of the protective network.
would be desirable to keep capacitance well below
1 µ F to keep the delay from exceeding ten seconds.
DESIGN
CONSIDERATION
FOR
FCC
Normal Operation. If the CH1804/A or the CH1809/A
CONFORMANCE
is the only device on the telephone line, leakage and
The CH1804A/9A products include circuits that couple
differential capacitance will tend not to affect normal
to the phone line and provide FCC required isolation
operation, since the line capacitance in the central
and protection.
The following guidelines should be
office or the local loop are minimal. The more devices
followed to maintain the conveyed FCC Part 68
that share a given local loop, such as modems and
registration:
extension telephones, the greater the capacitance and
leakage possibilities. Sources of capacitance, when
1) CH1804A/9A must be mounted away from
On-Hook, include ring detection circuits in modems.
hazardous voltages.
2) Connection of the CH1804A/9A devices to PSTN
lines should be made through a standard RJ-11C
jack or another approved connector device.
3) Circuit board traces to the CH1804A/9A TIP and
RING pins must have a spacing of greater than
0.10 inch from all adjacent traces. TIP and RING
traces should have a width of 0.020 inches.
Figure 2. Application Diagram indicating external
4) TIP and RING traces should be as short as
components to increase output drive, decrease
possible to prevent coupling to other signals lines.
false line cut indications and provide additional
Mount the CH1804A/9A as close to the telephone
overvoltage protection.
line connection as possible.
2003 Cermetek Microelectronics, Inc.
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Document No. 607-0015 Revision C (05/03)
Cermetek Microelectronics, Inc.
CH1804/A and CH1809/A
5) The registration label included must be affixed to
If Problems Arise: If any of your telephone equipment
the outside of the host product.
is not operating properly, remove it immediately from
the PSTN line, as it may cause harm to the telephone
network. If the telephone company notes a problem,
USER MANUAL
they may temporarily discontinue service.
When
The following information should be provided in the
practical, they will notify you in advance of this
host product user manual.
disconnection.
Type of Service: The (insert product name) is
designed to be used on standard device telephone
Table 2A. CH1804/A Pin Description
lines. It connects to the telephone line by means of a
PIN
DESCRIPTION FOR CH1804/A
standard jack called the USOC RJ-11C (or USOC
1
TIP 1 –Telco 1
RJ45S). Connection to telephone-company-provided
2
RING 1 –Telco 1
coin service (central office implemented systems) is
3
N.C.
prohibited. Connection to party lines service is subject
4
Out 1 –Active High Output 1
to state tariffs.
5
V CC – 5 Volts ± 10%
6
Gnd –Ground
Telephone Company Procedures: The goal of the
7
N.C.
telephone company is to provide you with the best
8
N.C.
service it can. In order to do this, it may occasionally
9
N.C.
be necessary for them to make changes in their
equipment, operations or procedures.
If these
10
N.C.
changes might affect your service or the operation of
your equipment, the telephone company will give you
notice, in writing, to allow you to make any changes
Table 2B. CH1809/A Pin Description
necessary to maintain uninterrupted service.
PIN
DESCRIPTION FOR CH1809/A
1
TIP 1 –Telco 1
In certain circumstances, it may be necessary for the
2
RING 1 –Telco 1
telephone company to request information from you
3
N.C.
concerning the equipment you have connected to your
4
Out 1 –Active High Output 1
telephone line.
Upon request of the telephone
5
V CC – 5 Volts ± 10%
company, provide the FCC registration number and
6
Gnd –Ground
the ringer equivalence number (REN); both of these
7
Out 2 –Active High Output 2
items are listed on the equipment label. The sum of
8
N.C.
aII of the REN’s for a given PSTN line should be less
9
TIP 2 –Telco 2
than five to ensure proper service from the telephone
10
RING 2 –Telco 2
company. In some cases, REN=5 may excessive.
2003 Cermetek Microelectronics, Inc.
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Document No. 607-0015 Revision C (05/03)
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CH1804/A and CH1809/A
Table 3
CH1804/A and CH1809/A Electrical Specifications
V CC =5 ν ± 5%
T A =0 to +55 ° C
Parameter
Symbol
Conditions
Min.
Typ.
Max.
Units
LOGIC
Output HIGH
V CC
I OH =0.05µA
2.4
V
Output LOW
V CC
I OL =2.0mA
0.4
V
TELEPHONE LINE
INTERFACE
M ohms
Input Resistance
R
TIP or RING to any other pin
8
Surge Protection
Conforms to all FCC Part 68 surge, hazardous
1500
V
voltage, and leakage requirements
V Input
Voltage required between TIP and RING to
2.6
(CH1804/1809 only)
V I
cause a Cut Line Indication
V
V Input
V I
Voltage required between TIP and RING to
20
32
V
(CH1804A/1809A)
cause an Off-Hook Indication
Leakage Current
I LK
Leakage to TIP or RING
±0.1
µA
Detection Time
T D
CX=0.001 µF (TIP or RING to GND)
1
sec
V CX =50V (TIP to RING)
FCC REGISTRATION
Label Supplied with Unit
Ring Equivalence
I CC
0.0A
REN
Power
+5V Supply Voltage (CH1804/A, CH1809/A)
0.3
1
mA
2003 Cermetek Microelectronics, Inc.
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Document No. 607-0015 Revision C (05/03)
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CH1804/A and CH1809/A
Table 4. Summary CH1804/A and CH1809/A Family of Products
Model
Summary of Features
Operating Temperature
CH1804
Cut Line Detector. Single Line, FCC Part 68 Approved, UL1459
0°C to 70°C
Listed.
CH1809
Cut Line Detector.
Dual Line, FCC Part 68 Approved, UL1459
0°C to 70°C
Listed.
CH1804A
Off-Hook Detector. Single Line, FCC Part 68 Approved, UL1459
0°C to 70°C
Listed.
CH1809A
Off-Hook Detector.
Dual Line, FCC Part 68 Approved, UL1459
0°C to 70°C
Listed.
Figure 3. CH1804/A and CH1809/A Physical Dimensions
Cermetek reserves the right to make changes in specifications at any time and without notice. The information furnished by
Cermetek in this publication is believed to be accurate and reliable. However, Cermetek assumes no responsibility for its use, or for
any infringements of patents or other rights of third parties resulting from its use. No license is granted under any patents or patent
rights of Cermetek.
Printed in U.S.A
406 TASMAN DRIVE | SUNNYVALE CA 94089 | LOCAL: 408-752-5000 | TOLL FREE: 1-800-882-6271 | FAX: 408-752-5004
CERMETEK WEB SITE: http://www.cermetek.com | EMAIL: sales@cermetek.com
iModem Network WEB SITE: http://www.imodem.net/ or https://sunnyvale.imodem.net/
2003 Cermetek Microelectronics, Inc.
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Document No. 607-0015 Revision C (05/03)