CH1804 View Datasheet(PDF) - Cermetek Microelectronics
Part Name
Description
Manufacturer
CH1804 Datasheet PDF : 5 Pages
| |||
CH1804/A and CH1809/A
Family of Line Detection and Monitoring Products
INTRODUCTION
The CH1804/A and CH1809/A are line status
detectors that are used to monitor line off-hook status
for shared lines, or to detect a severed or cut
telephone line. The CH1804/A is a single line monitor.
The CH1809/A is a dual line device allowing two
telephone lines to be monitored simultaneously and
contains two CH1804/A circuits (See Figure1). For
ease of convertibility, both devices share the same pin
out configuration.
The primary application for CH1804 and CH1809
products are security systems where detection of
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
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
below 20VDC thereby detecting an off-hook condition.
Since the CH1804A/9A products access the PSTN
system, FCC Part 68 approved is required. Cermetek
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
operate on a single 5-volt supply and provide a
separate active high indication when either of the two
attached lines is cut. The product is contained in a
single in-line package 1.0” long and 0.5” high,
requiring minimal PCB area.
Off-Hook Detection. The CH1804A and CH1809A
detector circuits will indicate an Off-Hook condition
when the voltage between the TIP and RING drops
below 20.0VDC. The Off-Hook condition is indicated
by the CH1804A (CH1809A) when the output of OUT1
(OUT2) is > 3.5V.
Cut Line Detection. The CH1804 and CH1809
detector circuits will indicate a Cut Line condition when
the voltage between TIP and RING drops below
2.6VDC. The Cut Line condition is indicated by the
CH1804A (CH1809A) when the output of OUT1
(OUT2) is > 3.5V.
FEATURES
• FCC Part 68 approved with conveyed registration.
• Usable on public switched telephone lines and wet
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.
Table 1. Features Available By Product.
Detection
Number of Lines
Feature CH1804 CH1809 CH1804A CH1809A
Cut Line
1
2
Off-Hook
1
2
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
2.2µF capacitance to ground. This is provided to filter
out zero crossing pulses which can occur during
ringing. Refer to Figure 1.
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)
between the output and 5 volts. However, this will
allow zero crossing pulses to occur. If more drive
current is needed while retaining zero crossing
filtering, an external capacitor must be added to
preserve the original RC time constant. See Figure 2.
Figure 1. CH1804/A, CH1809/A Functional Block
Diagram
ISOLATION REQUIREMENTS
For maximum detection flexibility, incoming telephone
lines should not share a common TIP or RING line. In
addition, the ground of the PSTN system should not be
common to the ground of the system where the
CH1804A/9A is installed. If either of these conditions
2003 Cermetek Microelectronics, Inc.
Page 1
Document No. 607-0015 Revision C (05/03)
Share Link: 