A SWITCH PATTERN RELAYS 700830

Diagram Notes AT 71214 - ISS1

Other

AT 71228

AT 71316 - A Switch Pattern Relays for Mark II and Mark III augmentation

AT 71414 -A-Switch Pattern Relays TXE 2

AT 71611 - A-Switch Pattern Relays Pentex TXE 2

TXE2 'A' Switch Pattern Relays

This equipment is designed to give test and mark wire access between the B Switches and the B Switch Selector, in response to a signal from a line unit.

Two units are used to mount the equipment. They are provided on a per A Switch group basis and are not duplicated.

The simplified block schematic to the left diagram shows the A Switch Pattern Relays with the associated equipment.

FACILITY SCHEDULE

Provision is made for:-

(1) Extending one of 25 combinations of 5 test Wires and 5 associated mark wires out of 25 test wires and 25 mark wires, in response to one of 25 pattern signals.

(2) Sending a 'major' signal to the C Switches.

(3) Detecting a permanent pattern signal caused by a welded MK relay contact in the subscribers' line circuit and A Switch. A prompt alarm is given, both alarm lamps glow on the alarm indicating panel, and the faulty pattern lead is earthed at the subscribers' line circuit and A Switch. No further faults can be detected by the A Switch Pattern Relays.

(4) Busying out an A Switch when a short circuit diode is detected in an A Switch, and giving a prompt alarm. Both alarm lamps glow on the alarm indicating panel.

(5) Busying subsequent access to a B Switch from a particular A Switch group when a short circuit diode has been detected in the B Switch, and giving a prompt alarm. The B Switch fault lamp glows and also the alarm lamp on the alarm indicating panel.

(6) Preventing more than one A Switch in an A Switch group from being busied out of service if more than one diode fault is detected.

(7) Preventing all B Switches in a particular major group from being busied out if more than one diode fault is detected.

(8) Detecting if an M relay contact welds in the A Switch Pattern Relays. When this occurs a prompt alarm is given, the alarm lamp and Switch Fault lamp glows, and the A-B link availability of the exchange is reduced to 4.

(9) Service to be maintained to all subscribers ln the event of a fuse blowing ln one of the units.

(10) Preparing a circuit for the A/B link congestion meter.

NOTE. References to the subscribers' line circuit and A Switch also apply to the Preference Control Circuit and Remote Junction Switching Equipment where these are fitted.

CIRCUIT DESCRIPTION

3.1 The Pattern Signal

When a subscriber's marker relay operates, a negative battery is connected to one of 25 pattern wires. The way in which the signals to the two units are divided is shown in the sketch.

The relationship between the Pattern number and the A-B links is shown in the table above

The AM-Lead Connections

'A' SWITCH PATTERN RELAYS AT71014

25 Sets of M & AP relays are contained on two plug in units which together form one set of APR's and serves one A switch group.

In a fully equipped major there will be three such sets of APR's

The function of the A pattenr relays set is to extend the test and mark wires of the 5 A-B trunks proper to A switch, to the B switch selector. The Appropriate APR's are operated by a -vb battery signal on the PN lead from the Subs Line Unit, which accomodates the calling or called subscriber.

It shoul dbe noted that each subs line unit has its own PN lead, each line unit will operate a differnet set of fie AP relays subject to the opverall pattern which requeires that there will always be one relay in each of the ranges:-