Having secrecy in parallel telephones
Often a need arises for connection of two telephone instruments in parallel
to one line. But it creates quite a few problems in their proper performance,
such as overloading and overhearing of the conversation by an undesired person.
In order to eliminate all such problems and get a clear reception, a simple
scheme is presented here (Fig. 1).
This system will enable the incoming ring to be heard at both the ends. The DPDT
switch, installed with each of the parallel telephones, connects you to the line
in one position of the switch and disconnects you in the other position of the
switch. At any one time, only one telephone is connected to the line. To receive
a call at an end where the instrument is not connected to the line, you just
have to flip the toggle switch at your end to receive the call, and act as usual
to have a conversation. As soon as the position of the toggle switch is changed,
the line gets transferred to the other telephone instrument.
Mount one DPDT toggle switch, one telephone ringer, and one telephone terminal
box on two wooden electrical switchboards, as shown in Fig. 3. Interconnect the
boards using a 4-pair telephone cable as per Fig. 1. The system is ready to use.
Ensure that the two lower leads of switch S2 are connected to switch S1 after
reversal, as shown in the figure.
Title: Having secrecy in parallel telephones
electronic circuit
Source: www.electronic-circuits-diagrams.com
Published on: 2005-02-09
Reads: 649
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