Menvier Security TSD401 Uživatelský manuál stáhnout pdf (Strana 18)

Menvier Security

Kenn Road Clevedon Avon BS21 6LH

Tel 01275 870078 Fax 01275 343453

E.Mail http//:www.menviersecurity.co.uk

TECHNICAL BULLETIN

GEN/001/93

LINE FAULT MONITORING

Different digicoms use various methods of Line Fault monitoring. This technical bulletin will

describe the various methods available, but will not address remote line monitoring as used on

Direct Line systems or REDCare.

LINE VOLTAGE MONITOR:

This monitoring method is used on older products and merely checks that a healthy line

voltage is present on the telephone line. This voltage is nominally 50 volts, which drops to

below 35 volts when a parallel handset is taken off hook, and will drop to 0 volts if the line is

cut. With newer, digital exchanges, it is possible to detect line voltage even on an inoperative

line.

The DC54 / DC58 / DC58M digital communicators signal off hook and cut line as a line fault

when selected as HI security.

When selected as low security the DC54 / DC58 / DC58M will only signal line fault on a cut

line.

RINGING IN MONITOR:

This technique continually checks for presence of ringing to detect whether an attempt is being

made to "jam" the phone line.

This type of monitoring is also used on the DC54 / DC58 / DC58M digital communicators in

addition to the Line Voltage Monitor.

TEMPORARY OUT OF SERVICE:

This technique offers the highest security of the three methods in that it seizes the line at

predetermined intervals, seizes the line and dials all but the last digit of the recipient's

telephone number and tests for the number unobtainable tone. This type of monitoring is used

on the DC54 / DC58 digital communicators in addition to the Line Voltage monitor and the

Ringing In Monitor. The line test interval period can be selected between daily to fortnightly, or

can be disabled.

Line Fault monitoring is only necessary when a bell delay time is programmed into the control

panel.

THREE WAY CALLING

When the DC58 / DC58M is triggered the unit checks for incoming ringing or off hook. The

digicom then sends a “Recall “ signal which is detected by the exchange as a request for a

new line. With a new line available the DC58 / DC58M then attempts to connect with the

Central Station.

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Menvier Security TSD401 Uživatelský manuál Strana 18