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| HT18_07 Datasheet, PDF (1/4 Pages) Supertex, Inc – Electronic Telephone Line Switch | |||
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HT18/ HT19
Electronic Telephone Line Switch
Features
⺠350V breakdown voltage
⺠18⦠maximum switch resistance
⺠Current limiting protection
⺠Operates at 2.3V input
Applications
⺠Telephone handsets
⺠Modems
⺠Fax machines
⺠Answering machines
⺠Remote meter reading
⺠Telephone interface products
General Description
The Supertex HT18LG and HT19LG are electronic line switch
circuits that replace the mechanical hook switch contact or a
discrete hook switch in a telephone handset or modem. They
switch the positive side of the telephone line using control
inputs that are referenced to the negative side of the line. In
their off state, they can withstand 350V on the positive input.
In their on state, they have a maximum series resistance of
18â¦.
The devices provide current limiting determined by an
external resistor. There are three control inputs. The HKS
pin turns on the hook switch when connected to the TPG
pin. This can be accomplished by using a mechanical switch
which closes when the handset is physically off-hook. The
LS pin allows a logic signal to turn on the hook switch. The
dial pulse, Pin 6, is used to turn the hook switch off for pulse
dialing. For the HT18, the dial pulse is active high (DP),
whereas for the HT19, it is active low (DP).
Typical Application Circuit
Tip
Transient
Protection
Ring
TPG
TP
RSEN
HT18
HKS
or
CS
HT19 LS
15V Telecom
Circuit
DP/DP
GND
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