User`s manual

VoIP/(802.11g) ADSL2+ (VPN) Firewall Router
Chapter 4: Configuration
111
Advanced – PSTN Environment Adjustment
PSTN Environment Adjustment options will help you to adjust the onhook and offhook voltage detection
values for your environment. You should use these if the default values are incorrect and result in PSTN
calls not being detected properly, e.g. calls being terminated within 5 seconds of being answered.
The actual levels are determined by your environment including the number and type of telephones used.
The PSTN line voltage checks should be made using the phones connected to the Phone Ports of the
Router.
OFFHOOK Setting
The purpose of this setting is to ensure that the Router can accurately detect when a phone is in use.
The OFFHOOK line voltage will vary between different phones due to differences in their internal circuitry.
The voltage may also vary over time from its initial value when the phone is first connected to the line.
To take your phone OFFHOOK, lift the receiver then press Hook/Flash until you hear your normal PSTN
dialtone, not your VoIP dialtone.
Wait several seconds and then press OFFHOOK Check Level.
Note: ONHOOK means hung up, OFFHOOK means in use.
You should check the OFFHOOK value for each telephone you have connected to this device. Set the
OFFHOOK voltage to the lowest setting registered for all your telephones, e.g. if your telephones return
values of 4, 5 and 7 then you should set your OFFHOOK voltage to 4.
Default value is 4 volts.
Note: The detected values will not automatically be set by the Check Level function; you must enter the lowest level
detected after testing all your telephones.
ONHOOK Setting
The purpose of this setting is to ensure that the Router can accurately detect when the phones are not in
use.
Some phone equipment uses the line voltage to charge internal batteries and similar functions by taking a
small current from the line when the phone is not in use. This will result in the line voltage being reduced
from the normal value. Note there is often a delay between hanging up the phone and the charge circuit
operating.
To check the ONHOOK voltage setting, ensure that all phones are hung up. Click on the ONHOOK Check
Level button and note the reading. Normally this reading will be around 50 volts.
Ensure that the phones have all been hung up for several minutes before checking the level.
Line fault conditions can have a similar effect in reducing the ONHOOK voltage.
The ONHOOK voltage should be set to a value lower than the test level. The default value is 18 volts and
will not normally need to be altered.