TMC KT1 Series, Руководство пользователя

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56 The message waiting option comprises R1 5,
PLG, SKG, PLH, SKH and lamp LP1. 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.
5 7 The bell capacitor circuit C 1 0 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.
58 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 BC 2,
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 instrument) to
increase volume.
59 When a Texas TCM1 512P IC (IC2) is used for
the tone caller, R21 and XL2 are omitted.
Components R14, R19, R20, 017 and C11 are
omitted when IC2 is a Ferranti device. C9 is then
changed to 22 µf, 40V.
60 For a timed break recall option, TR2, R9 and link
H are fitted, links K, M and N are omitted. Switch
S 1 2 is operated by the R (recall) key. For earth loop
recall, TR2, R9 and link Hare omitted, whilst links K,
M and N are fitted. On the basic version, with no
recall facility, links M and N are fitted, links Hand K,
R9, S 1 2 and TR2 are omitted.
61 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 the KT1 or KT4
telephone with a KBX 1 0 or KBX 1 00 system, fit SKB
to pins 2 and 3 of PLB.
62 In the circuits associated with IC1, R8, C4, 02
and 01 6 are not required for initial units, but these
positions are available for possible future
developments.
63 Most of the line current flows down the base of
TR2 (if fitted, see paragraph 60) and through TR 1 .
TR2 is then saturated in the on state. TR1 provides
current amplification during speech periods as it is
configured as a current source in series with the
loop. TR 1 and TR2 are switched off during timed
break recall if this option is installed. Capacitor C2
maintains the positive supply rail for IC 1 under such
circumstances. If TR2 is fitted, R9 is required to
3513 300 05070
9
provide a small bias current which is used to start up
the circuit.
64 The signal from the microphone is amplified by
about 24dB by the IC microphone amplifier which is
of a special low noise design. This amplifier also
provides a d.c. level-shift function which is applied,
together with the amplified microphone signal to the
base of TR1.
6 5 The signal from the line is obtained via an
attenuator R7 and R3 and is fed into the earphone
amplifier via C7 where it is summed with the
sidetone signal from the microphone amplifier to
provide sidetone cancellation. The earphone amplifier
output stage consists of a large enhancement
transistor with an active driven load to provide the
drive required by a 600 ohm earphone.
66 Both the microphone and earphone amplifiers
have a line displacement gain which is controlled by
the AGC control system. This circuit takes a voltage
from the d.c. control block which is similar to that
found on the base of TR 1 and compares it with a
voltage reference multiplier circuit.
67 Operation of any of the twelve keypad
pushbuttons causes the circuit to change from
speech to tone mode. The on chip oscillator oscillates
at the parallel resonance of XL 1, which is 560kHz.
The microphone and receive paths are switched off,
but a small signal is fed from the tone generators to
the earpiece, (confidence tone). The duration of any
tone is a minimum of 70ms but will remain for the
duration of the pushbutton operation. There is a
70ms 'silent' period at the end of each tone, when no
tones or speech can be sent.
68 Links
D
and F are not currently required, but
provision for their incorporation caters for future
development. Link Eis fitted only when tone levels of
-6 to -8dB are required.
69 Link R is omitted for KT 1 Series telephones,
whilst R4 is omitted for the KT
4
Series. C3 is to be
0.68 µf if the microphone is to ONT2002-002-
01 99, Issue 6, 0.4 7 µf if the microphone is to
ONT2002-002-0199, Issue 7, or 0.22 µf for KT4
Series telephones.
70 C14 is used to trim the value of C1. If C1 is 2.4
µf, C 1 4 is fitted. C 1 4 is omitted if 2. 7 µf is used for
C1.
(Figure 5)
KT1 and KT4 (1503) MF (Multi-Frequency) Version
71 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