TMC KT1 Series, Руководство пользователя

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necessity to reduce the earphone amplifier power
consumption). The chip can store up to 18 digits in
its memory, whilst signalling at any given time.
29 During signalling, the circuit may be subject to
line breaks caused by the exchange and these should
not interfere with the signalling. It is therefore
necessary for the circuit to reorganise these and to
conserve the power stored in C2 until the power
returns. However, should the break last for more
than a given period, it must be interpreted as a hook
switch down action and therefore return to speech
mode. The chip contains a line break detector which
compares Vdd with the voltage at the emitter of TR2
and should the latter be of a lower voltage, the circuit
will assume it is a break and switch off TR 1 and TR2.
The break is timed by the logic which resets the
circuit to speech mode if the break lasts for more
than 1 80 ms. Should the power return before a
period of 1 80 ms, the circuit will continue to pulse
out.
30 On very long lines, Vdd may not be high enough
to maintain the operation of the logic during impulses
and line breaks if the normal d .c. function were to be
applied. For this reason, a minimum Vdd regulation is
included which prevents Vdd dropping below a given
value before impulsing commences.
31 Links D, E and F set the impulse speed and ratio
according to the following:
Speed Break/Make Ratio Fit Link
10 p.p.s. 2: 1 E
10 p.p.s. 1. 55: 1 D
20 p.p.s. 2: 1 F
32 At the end of the signalling mode of operation,
the microphone amplifier is switched on and the
earphone amplifier is ramped back to normal again.
Once the sequence is complete, the oscillator is
switched off.
33 For KT1 Series telephones, link M is omitted,
C3 to be 0.68µf if the microphone is to DNT2002-
002-01 99, Issue 6 or 0.4 7µf if the microphone is to
DNT2002-002-0199, Issue 7. For KT4 Series
telephones, R4 is omitted, C3 to be 0.22µf.
(Figure 3)
KT1 and KT4 (1503) LD (loop Disconnect) Version
34 The PCB is connected to the line via the
following line cord terminal pins:
Pin 1 - To optional message waiting lamp
circuit
Pin 2 - B wire
Pin 3 - Bell input
Pin 4 - Earth Loop Recall (return)
351 3 300 05070
7
Pin 5 - A wire
Pin 6 - Not used
35 The A and B wires (nominally 24V, 48V or 60V
d.c. lines), are routed via the polarity bridge 09, D 1 0,
D 1 2 and D 1 3. The polarity bridge, including surge
suppressor, 011, a 130 V Zener diode, also provides
transient protection. C1 5 is not fitted, but its space
provides for possible future development.
3 6 The message waiting option comprises R 1 8,
PLG, SKG and l.e.d. 022. This option is most useful,
in say an hotel where the operator has received a call
for a guest but has been unable to contact him. The
operator can remotely activate the message waiting
lamp which is directly connected to the line cord, to
act as a reminder that a message is waiting to be
collected.
37 The bell capacitor circuit, C17 and PLC/SKC, is
fitted
in installations not using wall socket
capacitors. The circuit provides protection from
transient spikes, and is used as an anti-tinkle device
to prevent other telephones ringing during dialling
operations.
38 The tone caller capsule is fitted to the base of
the instrument and connected to the PCB when the
instrument is correctly assembled via BC 1 and BC2,
which are tin plated bridge contacts. The tone caller
capsule is fitted with an adjustable volume control
(attenuator), which should be turned clockwise
(when looking at the base of the telephone) to
increase the volume.
39 The tone caller circuit is centred on a TMC
1 503 integrated circuit. 020 and 021 are provided
for future development and are not currently used.
Links K and L, although currently fitted, allow for
further future development. Components SKD, PLD
and R 1 7 are omitted and link M is fitted for British
Telecom versions. Conversely, for commercial
applications, link M is omitted and SKD, PLD and R1 7
are fitted. R 1 7 in the circuit will reduce the volume of
the tone called by 1 OdB.
40 For the timed break recall option, links F and G
are fitted, and links Hand
J
are removed. Switch S11
is operated by the R (Recall) key. For the earth loop
recall option, links H and
J
are fitted and links F and G
are removed. All these links and S 11 are omitted in
the basic version.
41 Link A is not fitted on commercial versions of
KT1 and KT4. For 200 x 200 ohm feeding bridge
systems, fit SKB to pins 1 and 2 of PLB. For some
overseas installations using 400 x 400 ohm feeding
bridge systems and when using KT 1 or KT 4
telephones with a KBX 1 0 or KBX 1 00 system, fit
SKB to pins 2 and 3 of PLB.