See also Response 400

The BT Response 200 is a modern processor controlled, combined push button telephone, single tape answering and recording machine with remote interrogation.  The instrument may stand on a flat surface or desk top provided by the customer, or be wall mounted if required.  To wall mount, the bracket on the base is turned around so that the key hole slots face towards the top of the instrument.  Two fixing screws must be provided which will locate in the key hole slots.

The facilities for the instrument are as follows:-


  • Desk or Wall mounted. Lug on case provides off hook position for handset when wall mounted.
  • Loop or MF4 Signalling. Switchable by the user.
  • Mixed signalling. If set for LD signalling, pressing * (star / tone button) will change signalling to MF4 until call is cleared.
  • Recall. Earth Loop / 100mS timed Break. Switchable by user.
  • Last number Redial. Up to 32 digits. A pause, * (star) or recall signal counts as a digit.
  • Transfer Redial memory to permanent memory.
  • Latching Secrecy Button with LED indication.
  • Dial Pause, 4 seconds. (Pause button is under tape compartment cover)
  • Memory Stores. 3 one touch and 10 indirect (1 to 0 under keypad) . Up to 16 digits inclusive of any signalling change, pause and TBR recall instruction. Note:- Memory stores are protected by line power and will be retained for up to one hour when disconnected from line.


  • Message Tape. Standard MC-60 Microcassette. Up to 30 minutes recording time.
  • Normal Outgoing Announcement (Answer & Record) - Up to 2 minutes.
  • Answer Only Announcement - Up to 30 seconds.
  • Outgoing Announcement
  • Automatic soft switch to Answer Only when the message tape is full. An Answer Only Announcement must be recorded to use this facility, otherwise the machine will not answer making remote interrogation impossible.
  • Memo, Up to 30 seconds with separate LED indication, replay and pause facility.
  • Built in microphone - Used for announcement and Memo recording
  • Play messages - Press Play, to Pause press Play again. To play all messages to end of tape, press Play twice more when tape has stopped.
  • Incoming Message up to 3 minutes.
  • Skip Announcement - Frequent callers can key '*' from an MF4 telephone or remote interrogator and leave a message without having to listen to the outgoing announcement.
  • Single digit LED display - 1 to 9 messages or machine status. 9 flashing indicates more than 9 messages.
  • Volume Control - From minimum to maximum volume.
  • Call Screening (Monitoring) - Listen to incoming callers leaving message. The volume control must be turned up to listen.
  • Two way recording. A security tone is given every 15 seconds.
  • Automatic Message Save when interrogated remotely.
  • Fast Message tape Forward, Rewind and Erase.
  • Cleared Detect. Line break stop. Clear Detect switch ON or OFF.
  • VOX - (Voice Operated Switch) release from line. Low or High sensitivity switchable by customer. Sensitivity switch LO or HI.
  • Ring Adjuster - 2, 6 or TS (Time Saver). TS = Answers after 2 rings if messages have been left, or 6 rings if no messages. This facility aids remote interrogation. i.e. When interrogating remotely, if the call is not answered after 2 rings, the caller can clear down knowing there are no messages and save the cost of a call.
  • Remote set to Answer - Call machine and let it ring 20 times.
  • Branchphone reset - Will release machine from the line should a parallel telephone handset be lifted. Inhibited for a short period (3 seconds) before and after answering.
  • Paytone Detection - Up to 15 seconds delay of announcement if paytone is present.
  • Remote Interrogation with a preset 2 digit security code.
  • The customer may keep a library of tapes that have been pre recorded with different announcements. The tape must be changed with the machine POWERED UP for correct operation.

The handset and keypad are line powered.  The answering / recording features of the instrument is mains powered from the 9.5 volt dc plug top transformer.

In the event of a mains failure all mains dependent facilities cease to function.  Restoration of the mains supply will automatically reset the machine to answer whether or not it was set to "answer" before the supply failed.

This is a system default condition and cannot be overridden. Messages received before the power failure are not lost and can be played back remotely or by using the play button on the machine.

Made by Inventa Electronics

BT supplied on a Sale basis only.

Approval Number S/2981/3/L/502 010
Approved DEL, PBX CAT 12 3, 5 & 7.

Approved as supplied for connection to Public Switched Telephone Networks (PSTN) and 2-wire PBX extensions.

Phone Socket and a 240 volts, 13 amp, 50 Hertz mains supply socket are required within easy reach of the instrument.  Transformer lead and Line Cord both measure 3000mm.
Suitable for use on Phone Socket installations on DELs and most types of 2- wire PBX extensions.
Ringer Equivalence Number (REN) is 1.

If the machine fails completely, the output voltage of the Transformer should be checked. The Transformer output is marked 9.5 volts dc, but will measure about 13 volts when tested with the output open circuit.

The User Guides recommend that the customer should perform the following routines:-

Every three months, turn the tape over and rerecord the outgoing announcement.
Every six months, clean the tape head using a cotton bud moistened with a proprietary tape head cleaning fluid and replace the tape.  Any high quality "normal bias" MC-60 size Microcassette is suitable.  Although available, longer and shorter tapes must not be used as they will prevent the instrument from operating correctly.

The duration between the above routines should be reduced if the machine is heavily used.

New units carry a 21 months warranty from the date of manufacture as shown on the year and week marking on the base of the instrument. These markings form the first 4 digits of the serial number.

DESCRIPTION                                                   BT Item Code
Response 200 Combined Telephone / Ans & Rec Machine           870469
(Complete with transformer and tape)
Transformer 9.5 volts dc                                      870471
BT Remote Controller No 2 (MF4)                               870427
Message Tape MC-60 Microcassette.                             870435
Or any high quality, normal bias MC-60.

Normal test conditions when waiting to answer.  After answering, the telephone and answering machine presents a loop resistance to line of approximately 3280 measured at 28mA. Additionally, the instruments will draw about 4.6ma on hook.  This may appear to give apparent Low Loop line test conditions.  With the handset off-hook, like many modern telephones, they may give high resistance telephone loop test conditions.


15 seconds to 2 minutes depending how many messages are recorded.

The ringing circuit has been designed to recognise both PSTN and all internal ringing cadences generated by BT PABXS. There is no manual ring facility.

3. VOICE / TONE DETECTION (Voice Operated Switch - VOX)
The VOX will release the machine from the line after approximately 7 seconds of quiet, constant or cadence Network tone (i.e. dial tone, NU etc).

The VOX sensitivity has a High and Low Sensitivity switch provided.  The normal switch position is High. In this position it is possible that line noise may be detected as speech.  If this happens the machine will record line noise up to its maximum message length.  A Low setting is therefore provided for use in cases where line noise causes persistent problems.

4. CLEAR DETECT Line Break Clear / Release from line
Modern exchanges generate a 100 ms line break on the called parties line when the calling party clears down, this is a called a disconnect clear signal.  The machine will detect this signal and immediately release from the line without the need to wait for network tones.

When the machine answers the line, it checks whether paytone is present.  If paytone is detected, the announcement is delayed for up to 15 seconds.

This facility causes the machine to release the line when a telephone connected to the same line is taken off-hook.  For about 3 seconds before and after answering this facility is inhibited. This prevents the false release of the machine from line due to line ringing (current surge to & fro) when answering.


Provides the facility for remote interrogation using a 2 digit preset security code.

Remote interrogation is achieved by using a BT Remote Interrogator or MF4 telephone to enter the security code any time after the machines have answered, and then further instructions as per the user guide.

On-site maintenance of the Response range is limited as the equipment contains no serviceable parts.  Some routine servicing - detailed in the User Guide should be carried out by the customer, but field maintenance is restricted to checking the facility switch settings and testing the power unit output.

Several adapters used with Response instruments are marked with lower outputs than those actually measured.  Approximate voltage readings (with the output open circuit) are as follows:-
Transformer 19B (marked 13.5V DC) measures 19 - 20v.
Transformer 752 (marked 9V AC) measures 11 - 12v.
Transformer 753 (marked 9.5V DC) measures 13 - 14v.


It has been reported that a large quantity of the Response range of TARMs have been returned as faulty without being fully reset and retried.  Some faults are caused by quick line disconnects and Radio Frequency Interference and may be cleared by a reset.

Models such as the Response 200, 300, 400, 500 & 1000 have all got a reset button on the underside of the unit.  Depressing this button momentarily, using a small probe, will perform a slightly different reset to that performed when the mains is turned off/on.  It is suggested that this is performed first, then retry all facilities, before changing out the unit.

However, if after changing the unit the same fault recurs on the new unit, the problem may be site specific and changing the unit again will be of no advantage.  If this is the case, please contact the Technical Helpdesk for further advise.

A major problem with Response TARMs recording after a message has been left has been caused by the exchange equipment presenting ‘clicks’ on the line when it is idle. This is due to a modified line card on System X exchanges.  BT Labs are aware of the problem and are investigating a cure.  Changing the unit will not clear this problem. 


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Last revised: December 19, 2010