VTEL VOICE & DATA MULTIPLEXERS
General Information
The system provides toll quality speech for two telephone lines and one
data service over a point-to-point radio link at a net rate of 19.2kbps. .
Voice Coding
The technology used is state-of-the-art digital voice encoding and
modulation to provide the best voice quality and be spectrum efficient at
the same time. Recently approved coding techniques (G.723) allow toll
quality with a bit rate of only 6.4Kbps.
The equipment is transparent to the user's telephone and supports both DTMF
and loop disconnect (rotary/pulse) dialing from the remote end without
alteration.
Pay Phones
It provides options for equipment to support payphone operation. Payphone
option includes provisions for 12 or 16 KHz SPM metering and/or polarity
reversal as needed.
Line Interface
The line interface equipment is capable of being configured for 2-wire
subscriber loop or 2-wire or 4-wire E&M by internal modules.
The equipment is compatible with FXO, FXS, 2 wire, 4 wire and hotline
systems by changing modules and/or internal jumpers and switches.
The audio response and general parameters conforms to CCITT specifications.
| Voice Channels Characteristics |
|
| Voice Channels |
Two |
| Digitizing Technique |
MP-MLQ, CCITT G.723 |
| Acceptable Channel Bit Error |
1x10-3 or Better Rate |
| Analog Interface |
2-wire FXO
2-wire FXS
2-wire/4-wire E&M |
| Fax Operation |
Fax relay |
| Fax Speed |
4.8kbps – voice rate 6.4kbps |
| Impedance |
600 ohm nominal |
| FXS Interface |
EIA RS-464, loop start |
| Nominal Impedance |
600 Ohms |
| Return Loss (300 to 3400 Hz) |
Better than 20 dB |
| Loop Voltage |
40V DC |
| Loop Current |
25 mA |
| Ringer |
50Vrms(±10%) |
FXO Interface
Off-Hook |
EIA RS-464, loop start |
| DC Impedance |
50 ohm |
| AC Input Impedance |
600 ohm |
Return Loss Better than
On-Hook |
22dB |
| DC Resistance |
0 to 100 VDC: more than 10M ohm |
| AC Impedance |
15.3 to 68 Hz, 40/150 Vrms: 20k ohm |
| Ringer Equivalence Number |
0.4 REN |
| Ring Detect Range |
40 to 150 Vrms, 15.3 to 68 Hz |
| Transformer Isolation |
1500 Vrms |
| DATA Channel |
RS-232 |
| Data Rate |
4800bps |
| E&M Interface |
|
| Signaling Interface |
EIA RS-464 Type I
Modified EIA RS -464 Type I,II,III,V
British Telecom SSDC5 |
| Analog Interface |
4-wire of 2-wire interface, strap selectable |
| AC Impedance |
600 ohms |
| Transformer Isolation |
1500 Vrms |
| Diagnostics |
Remote loop and BERT on the data channel,
or tone injection on the voice channel. |
System Description
The system consist of two main parts: The Exchange side MUX/DEMUX and the
Subscriber side MUX/DEMUX which are interconnected through a 2Mb/s PCM link.
Each of the above two parts comprises of following units:
1) Common Board
2) Line Interface card
- FXO card for Exchange side
- FXS card for Subscriber side
Products Feature
- 16 ports per line card.
- 2.048 MB/s E1 interface between Exchange and Subscriber side.
- Design according to ITU-T recommendations and ETSI standards.
- Extra back-up port.
- Supports CLIP, Loop reversal and Metering.
- Distinctive Ringing
- Feature transparency for all Switch features
|
ELECTRONIC
PRIVATE WIRE RELAY SET
(Physical & Channel)
Telenet’s Tropo CKT provide connection between two distant subscribers
over a potential free link. This CKT provides 2 interfaces one that can be
terminated to an analog Phone instrument or to the CO input of a EPABX on
the back plate the same is available on J1 . And the other end to the Tropo
input , the same available on J2 of the back plate.
Specifications
The Design of the Circuit is made very simple and rugged. It has been well
protected that under any kind of fault situation the main circuit
will be isolated and thus the restoration time can be in minutes.
1. The Speech Path is provided through the coupling transformer to allow
for maximum efficiency in the speech transmission and at the
same time totally isolating the two sides from their DC paths.
2. The Current Limit circuit is so designed that it
will restrict the current to less than 125mA. Even if the short is a dead
short, still the current will be limited with negligible heating
of the switching transistor which regulates the
current flow.
3. The Offhook / Onhook sense circuit is isolated from the line By use of
opto isolators.Thus at no point of time would any voltage surges or spikes
etc, can come on the side of the logic circuit. Thus the logic
circuit is adequately protected. Offhook is sensed on the
current flowing through the line.
4. Sealed Relays have been provided to feed ring
to the subscribers and isolating the circuit while the ring is
fed. To sense Offhook in ring a voltage comparator is used to
detect the offhook status of the subscriber.
5. The Logic Circuit is so designed that it will know all the states of
the system and will appropriately react to the change in
states. For eg if subscriber A ( analog phone ) lifts,
then TROPO will ring and A will get a ringback tone. If
the Tropo initiates a call , then the ring will be offered to the Subscriber
(analog phone )
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© , Telenet Systems Pvt. Ltd... All Rights Reserved
