Optical Fibre & 2W Line Block Telephone with Ringer


This is DTMF technology based telephone in compliance to RDSO Spec. No. (RDSO/SPN/191/2005) with dual media option (Quad / dark Optical fiber cable). The system is interchangeably workable on Quad cable (upto 30 dB channel loss that translates upto 15 Km typically) or on optical fiber (upto 5 dB channel loss that translates upto 15 Km typically). The media can be opted with a manual selector switch.

  1. The system uses single mode 1310 &1550 nm Industrial grade ruggedized transceiver.
  2. Input Supply: 24V DC nominal (+/-20%) @ 80mA
  3. Operating Temp.: -10o C to +70o
  4. SC type Fibre Connector

Transmitter & Receiver Section

The transmitter section consists of a 1310 &1550 nm FP laser in an eye safe optical subassembly (OSA) which mates to the fiber cable. The laser OSA is driven by a custom IC which converts differential input PECL logic signals, ECL referenced (shifted) to +5 V supply, into an analog laser drive current.The receiver utilizes an InGaAs PIN photodiode mounted together with a trans impedance preamplifier IC in an OSA. This OSA is connected to a circuit providing post‑amplifi­cation quantization, and optical signal detection.


The “DTMF based Electronic Block Bell & Block Telephone Equipment” serves

the purpose of both the conventional Block Bell Equipment and Block telephones

and will consist of the following items :

1) Tone & Speech Control Unit

2) Handset

3) Power Supply Unit (optional)

Tone & Speech Control Unit ” is housed in an Aluminum Cabinet. This unit will

generate standard DTMF tones, which will be transmitted through

through OFC (Dark Fibre) or Quad cable to the other end station where the tone will be decoded

and a piezo buzzer will be activated. The DTMF tones which are transmitted from the

Tone control unit from the other end station will also be properly decoded. This unit

may be housed inside the Control Panel of the Block instrument.

Tone & Speech Control Unit ”  also have proper speech amplifiers so that

trans and recv speech signals are of proper amplitudes.

Also have proper surge protection arrangement with “GDT, MOVR, Inductors and

PTC resistors  suitably connected to a proper “Earthing” terminal to avoid

damage due to lightning and other voltage transients.

Handset  with PTT switch  connected to the Tone & Speech control unit. The handset  meet the requirements as per specification no. IRS; TC – 37.

The cordage  connected with the handset on one end with the plug in type 5 pin connector on the other end for connection with Tone & Speech Control Unit .

Power Supply Unit” will have a 24V/7AH rechargeable maintence free battery and

charger and will be used to supply power to the “Tone & Speech Control Unit”. This

is an optional item and will be supplied if specially ordered by the Purchaser.

The “DTMF based Electronic Block Bell & Block Telephone Equipments” will be

connected back to back in “point to point” communication mode.

The telephone protected from Surge and Transients by using “GDT”, “PTC”

and “MOVR” based surge protection system.

The telephones work from DC Power source of 24 V DC + 20%, -30% with reverse polarity protection. 24V @ 80mA 


Power On” LED : “Power On” LED is of Green color which will be mounted on the

body of the Tone and speech Control unit . This LED will glow when 24V DC is

connected to the unit.

Call Indication LED : “Call Indication” LED is of Red color, which will also be

mounted on the body of the Tone and speech Control unit. This LED will glow when

the telephone is being called by the other end telephone.

A piezo buzzer will sound along with RED LED indication when the telephone is

being called. Duration of buzzer sounding will be 225 msec. +/- 25 msec.

The telephone set should be able to identify and produce sounds for repeated calling

signals as fast as 2 calls per second. (minimum call interval = 400msec).

The called set not sound continuously even if the push switch of the caller

telephone is kept pressed for a long duration.

Ring back Tone:

Ring Back Tone (RBT) will be available at the calling telephone when the other

end telephone rings. This is a confirmatory tone to confirm that the other end

telephone buzzer actually rings.

2 thoughts on “Block Telephone

Leave a Reply

Your e-mail address will not be published. Required fields are marked *