SYSTEM
100
SWITCHING TELEPHONE SYSTEM
SYSTEM 100 is a simple low-cost switching telephone system that
provides access to a single public-exchange or PABX line from up to four
telephones. Four variants - 101 to 104 - are offered to suit different
applications.
Typically, a system can be provided for a secretary and one or two executives.
The secretary can answer all incoming calls and transfer them to the executives
as required. The executive can dial all his own calls, although the secretary
can dial them for him if preferred. There is priority between telephones: when
an executive is using the exchange line, the secretary cannot gain access to it
- this ensures that an executive's calls are not overheard.
The system is also an 'intercom' between its telephones, and can
be used while an exchange call is being held (exchange and intercom calls are
secret from each other).
A single basic telephone type is used for all positions and can be installed
without removing the telephone case. A number of versions are available: keypad
or rotary dial; table or wall mounted. System operation
is by pushbutton switches in front of each telephone's handset: 'EXCHANGE' to
connect the telephone to the exchange line; 'HOLD', to hold an exchange call
while making an 'intercom' call to one of the other telephones; and '1' and '2',
to operate built-in intercom-calling buzzers in the other telephones. A lamp
lights on the telephone when the exchange line is in use.
Each system comprises telephones, a power unit (normally AC-mains energized, but
batteries can be used) to operate the intercom, lamps, and buzzers, and a common
facilities unit (CFU) to interconnect the exchange line, power supply, and
inter-telephone wiring. Alternative CFUs provide: visual indication of exchange
ringing; visual reminder that an exchange call is being held; and automatic
transfer of ringing to the executive's telephone if the secretary does not
answer the call within about 15 seconds.
TELEPHONES
Only one version of the System 100 telephone is required; it is based on the
standard GEC746 table telephone, and uses many common parts. Thus, stores
keeping and spares are simplified, and additional inventory requirements are
kept to a minimum. The detailed differences between the System 100 telephone and
the GEC746 are illustrated overleaf. The System 100 telephones are available in
a choice of three colours: dual-grey, ivory, and black.
Wall mounting
The telephones can be converted to wall mounting by inverting the dial or
pushbutton keypad assembly, fitting a handset-support bracket to the carrying
handle aperture on the telephone case, and fitting a wall bracket to the
telephone base. If desired, the four control keys can be replaced by keys with
inverted legends.
Variants
Four main variants are offered, which concern the signalling. The variants are:
-
Rotary-dial signalling at 10 IPS
-
Pushbutton 'dialling' with loop-disconnect signalling to the
exchange
-
Pushbutton 'dialling' with multi-frequency output
-
Pushbutton 'dialling' with DC-leg output
The rotary dial variant uses the standard dial assembly with a clear plastic
finger plate. The mechanism is a trigger type with a self-compensating action
which exhibits no appreciable variation in pulse ratio after 4'/2 million
impulses.
The three pushbutton variants are identical to the rotary-dial model, except
that the dial and ring are replaced by the appropriate key unit and escutcheon.
The loop-disconnect pushbutton variant is a direct replacement for the rotary
dial instrument. The dialled numbers are stored - using large scale integrated
circuits - and released to the exchange at the appropriate speed, normally 10
IPS. The dial electronic circuits are powered from the exchange battery.
The multi-frequency variant provides audio-frequency signalling to the exchange
(in accordance with CCITT Recommendation Q23): the dialling frequencies
transmitted over the telephone line are detected by special receivers at the
exchange. An individual combination of two frequencies is generated when a key
is pressed.
The fourth variant uses 'DC code C' signalling. It is a low-cost alternative to
the other types for P.A.B.X. or PAX with suitable detectors.
|
Rotary Dial |
|
|
Press Button Rotary |
OPERATION
SYSTEMS 102, 103, AND 104
EXCHANGE CALLS
An outgoing call is made from any telephone in the system by lifting the
handset, pressing the EXCHANGE button, and dialling. An incoming call rings the
bells at all the system's telephones and is answered at any telephone by lifting
the handset and pressing the EXCHANGE button.
Clear down
Replacing the handset clears the call and automatically releases the
EXCHANGE button (or the HOLD button, if the call has been held).
Secrecy
The normal wiring arrangement prohibits more than one telephone at a
time gaining access to the line. 'Line in use' When the exchange line is in use,
the lamp on each telephone is lit, and automatically switched off on clear down.
Other lamp indications that can be provided are described under CFU.
Ringer loudness
All telephones have a three-position volume control which
protrudes from the telephone base-plate. The lever can be modified so that it
also switches the bell off: one of the telephones in the system (usually the
secretary's) is not modified. Thus all incoming calls are answered by the
secretary, without disturbing the executive; but if the secretary is absent, the
executive telephone's bell can be switched on. An optional delayed-ring feature
is described under CFU.
INTERCOM CALLS
An intercom call is made by lifting the handset and momentarily pressing the
appropriate intercom-calling button ('1' or '2'). A call is answered by lifting
the handset, without operating a button.
EXCHANGE-CALL ENQUIRY OR TRANSFER
To make an intercom (enquiry) call to another telephone during an exchange-call
conversation, press the HOLD button (which releases the EXCHANGE button): this
connects the handset to the intercom circuit without releasing the exchange
call. An intercom call can then be set up (which is secret from the exchange
call). At the end of the enquiry, either telephone can be connected to the
waiting exchange call by pressing the EXCHANGE button on the appropriate
telephone; the handset is simply replaced at the other telephone.
PBX OPERATOR RECALL
To provide PBX operator recall (or to make use of a PBX enquiry-and-transfer
feature) button '2' is used: with the EXCHANGE button pressed, '2' applies an
unbalance to the exchange line and does not operate an intercom buzzer; with the
EXCHANGE button released (or the HOLD button operated), '2' is used for intercom
calling.
POWER SUPPLY
A local 10-12 V DC local power supply is used to operate lamps, buzzers,
intercom, and common facilities unit. Normally a wall-mounted AC-mains power
unit is used, although some systems can be operated from batteries: details are
given overleaf.
In the event of a local power supply failure, the system can still be used to
make and receive exchange calls, but
the other features are inoperative.
CFU: COMMON FACILITIES UNIT
The exchange line, inter-telephone wiring, and local power supply are
interconnected via a CFU. Different versions of the CFU can provide a number of
additional operating features: their application is tabulated overleaf.
Visual ringing
Each telephone lamp flashes in synchronism with exchange ringing
to provide a visual indication at all telephones, regardless of whether the
telephone bells are switched off.
Flicker hold
When an exchange call is held, each telephone lamp flickers as a
reminder.
Delayed ring
This feature provides an alternative to the standard 'bell off'
arrangement. A time delay is introduced between the onset of ringing and the
operation of one bell in the system. Thus, a secretary can answer calls without
the executive telephone's bell ringing: however, if she is absent, the executive
telephone's bell rings after a delay adjustable
between five and fifteen seconds.
SYSTEM 101
System 101 differs from the others in that one telephone terminates two exchange
lines. One line is allocated primarily for outgoing calls (it replaces the
intercom circuit), and the other for incoming calls. A call on the 'incoming'
line is answered, or made, after pressing the EXCHANGE button. To deal with a
call on the 'outgoing' line, it is not necessary to first Dress the EXCHANGE
button. This system does not use lamp. buzzer, local Dower unit or CFU.
DATA
SYSTEM TELEPHONE
The SYSTEM 100 switching telephone is based on the standard GEC746 instrument,
to which have been added the necessary pushbutton switches, lamp, and DC buzzer
to provide the operating features: the same telephone instrument type is used at
all positions in a system. Each telephone is provided with four switch
mechanisms. Many of the telephone components are standard GEC746 items,
minimizing stores holdings.
SYSTEM ELEMENTS
CHOICE OF TELEPHONES
Available in black, ivory, and grey; table or wall
mounted; rotary dial or pushbutton signalling.
Loop-disconnect signalling, using
rotary dial, normally 10 IPS - type 99480/colour/2
Loop-disconnect signalling, using pushbutton keyset, normally 10 IPS
- type
99480/colour/7
Multifrequency signalling, to CCITT Recommendations - type 99480/colour/3
CHOICE OF COMMON FACILITIES UNIT (CFU)
Type 98569 - wall mounted, 104 mm x 68 mm; incorporates terminal field, inductor
(for common intercom feed), and capacitor (for exchange ringing circuit).
Type 99502
- wall mounted, 134 mm x 84 mm; incorporates terminal field,
inductor, capacitor, and multivibrator to provide a lamp-flicker indication when
an exchange call is being held.
Type 99581 - wall mounted, 165 mm x 120 mm; incorporates terminal field,
inductor, capacitor, multivibrator, and a high-impedance ringing detector/relay
to provide lamp-flash indication in synchronism with ringing current. Also
incorporates a time out which removes a short-circuit from one or two bells in a
system after a delay adjustable from 5 to 15 seconds (at least one bell in such
a system always receives undelayed ringing).
CHOICE OF POWER SUPPLY
250-250v AC 50-60hz input, 10v DC output - type 97206
110/220-240v AC 50-60hz input, 10v DC output - type 99768
SUMMARY
Exterior
Case and handset moulded in ABS high-impact plastic.
Cords
PVC-covered cadmium-tinsel conductors. Held by stress-relieving grommets.
Line cord: straight; 2 m (78 in)
Handset cord: coiled; 200 mm (8 in) unextended, 1.7 m (68 in) extended.
Signalling
Choice of rotary dial or pushbutton keyset.
Dial: characters printed black on antique-silver background beneath a
clear-plastic finger plate. Trigger type with self-compensating action. Projects
through self-centring ring on the case. No appreciable variation in pulse ratio
after 4% million operations. Loop-disconnect signalling - impulse speed 10 IPS;
break-to-make ratio 2:1 (66%); inter-digit pause 240ms. Other speeds, ratios and
inter-digit pauses can be supplied.
Pushbutton keyset: 10 or 12 buttons, with black numerals on a white background,
arranged in the CCITT recommended 3 + 3 + 3 + 1 format with 'fall through'
action to ensure positive operation.
Choice of:
-
Loop-disconnect, Multifrequency,
or DC-leg signalling. MF and DC-leg signalling use 1 2-button keysets.
-
Loop-disconnect signalling: impulse speed 10 IPS, break-to-make ratio 2:1 (66%);
inter-digit pause 800 ms; other speeds, ratios, and inter-digit pauses can be
supplied. 18-digit store.
-
Multifrequency signalling: 2-out-of-7 frequency calling, to CCITT recommended
frequencies.
DC-leg signalling: ground (earth), high resistance, or low resistance applied to
each of three wires between telephone and suitably equipped PABX.
Transducers
Receiver inset: rocking armature; replaceable capsule: sensitivity +
56dB relative to 1 Pa/root w
Transmitter inset: carbon granule, replaceable
capsule; sensitivity -10dB relative to 1 V/Pa at 2 Pa input.
Regulator
A built-in automatic volume regulator limits speech-signal amplitudes on lines
shorter than 400f1 ; virtually no attenuation on longer lines.
Signalling
Exchange: double-coil ringer; DC resistance 1000 ohms; accepts ringing currents
between 16 and 30 Hz; bells, double gong, harmonizing tones; 3-position volume
control with optional 'bell off' position.
Intercommunication: DC single-coil
buzzer, moving armature type; DC resistance 55J1., A signal lamp is fitted to
each telephone to indicate when the exchange line is in use.
Power supply
10 to 12 V DC to operate buzzers, lamps, and intercommunication circuits. This
can be provided either by a GEC power unit or 12 V DC dry batteries. In the
event of a mains supply failure, the exchange line remains in service, but lamp
and buzzer indications and the intercom circuits are inoperative.
Environment
Suitable for all climates; protected against the entry of insects.
Dimensions and weight
Height: 119 mm (4.75 in) Width: 250 mm (10 in) over handset; 140 mm (5.5 in) over
case.
Depth: 216 mm (8.5 in) over case. Weight: 1.7 kg (3.5 lb) complete telephone;
230 g (8 oz) handset.
SYSTEM COMPLEMENT
Number of telephones
|
CFU type |
CFU optional features |
Power supply |
SYSTEM |
1 |
Not used |
|
Not used |
101 |
2 |
98569 99502 99581 |
None
Flicker hold
Flicker hold ' Delayed ring ' Visual ring |
Mains or battery
Mains or battery
Mains |
102A
102B
102C |
3 |
98569 99502 99581 |
None
Flicker hold
Flicker hold ' Delayed ring ' Visual ring |
Mains or battery
Mains or battery
Mains |
103A
103B
103C |
4 |
98569 99502 99581 |
None
Flicker hold
Flicker hold ' Delayed ring ' Visual ring |
Mains
Mains
Mains |
104A
104B
104C |
Taken from the GEC Catalogue Leaflet
1850/1077/278 (1978)