Quote:
Originally Posted by Dave Moll
Apologies, after checking one of my 704s, I find I have misremembered - it doesn't have a "monitor" function, just "CB" or "LB" for communicating with, respectively, the exchange or the subscriber's end.
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Not quite correct
I've just checked the Tele 704 I have on my GPO van and it does have the facility to monitor the line without looping it. It all depends on which model 704 you've got! Mine is the original Tele 704 marked as 'GPO Tele 704' on the top of the lid . By pressing the button on the handset it is possible to monitor the line without looping it - just tried but the switch has to be in the 'CB' position. Loops the line in the LB position. See the
'N' diagram N804
The Engineering Instruction for the Tele 704 states
2. PREVENTION OF INTERFERENCE TO WORKING CIRCUITS
When connecting the telephone to a pair in a cable that contains working circuits, prevent possible disturbance to a working circuit as follows:-
1.Set the three-position slider switch to the CB position and connect the telephone to line.
2.Press the transmitter CUT-OFF button on the handset before removing the handset from its cradle.
3.Check that the line is not in use.
3. AUTOMATIC EXCHANGE LINES
1.Check, as described in par 2, that the line is not in use.
2.If the line is not in use, release the transmitter CUT-OFF button.
3.Dial the required number.
The Tele 704 was superseded in 1973 by the 'PO Tele 704B' marked on the top and that has had an 82 ohm resistor fitted such that it kept the loop even when the microphone was disconnected. I assume that the same applies to the 'BT Tele 704C' which followed it - but that's too late for my van !