JPS6347033B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a connection method in a telephone device configured to multiplex and transmit a call signal, a control information signal, and a power supply current by multiple telephones connected to a pair of lines. It is related to.

In conventional telephone equipment, such as button telephone equipment, which is configured by multiplexing speech signals, control information signals, power supplies, etc. onto a pair of lines, the speech signal is transmitted in the baseband band, and the control information signal is converted to a high frequency band. It is generally transmitted as a In such a case, a separate filter is required to separate the call signal and the control information signal in order to prevent mutual influence of the signals, resulting in a problem that the configuration of the device becomes complicated. In addition, when the chiyoke coil inserted when transmitting and receiving power supply current is connected directly to the line, it needs to be a coil that does not become a line load in the communication signal band and control information signal band, and is large and has a distributed capacitance. Less is required, which worsens the economic effect. Furthermore, the power supply current
There is also a configuration in which the signal is transmitted and received after passing through the LPF, but in this case, DC superposition must be taken into consideration in the LPF coil, which has a low cutoff frequency, and the problem is that the coil becomes large.

The present invention solves this problem without providing individual filters to separate signals.
The present invention provides a connection method for a telephone device that allows a telephone call signal, a control information signal, and a power supply current to be separated from each other using a single simple transformer.

Hereinafter, the present invention will be explained in detail with reference to the drawings in comparison with a conventional example.

Figure 1 shows an example of a configuration using a conventional filter, where 1 is a line and 2 is a line that passes a telephone signal.
LPF, 3 is a communication circuit, 4 is a handset, 5 is an HPF that passes control information signals, 6 is a transmitting/receiving circuit,
7 is a control circuit, 8 is a choke coil, 9 is a power supply circuit, and 10 is one telephone in the button telephone device.

FIG. 2 is an embodiment of the present invention, where 11
is a transformer designed in the control information signal transmission frequency band. The primary side of the transformer 11 connected to the line 1 consists of two windings separated from each other at the midpoint potential, and the mutually separated terminals at the midpoint potential are connected to the communication circuit 3 and also to the chiyoke. 8
It is connected to the power supply circuit 9 via. Furthermore, FIG. 3 is a circuit diagram for explaining the structure of this transformer, where 12 and 13 are both primary windings, and 14 is a secondary winding.
This is the next winding. Here, the inductance of the windings 12 and 13 is L ₁ [H], and that of the winding 14 is L ₂ [H].

Generally speaking, the primary impedance of a transformer is reduced to Z ₁ by the lower limit frequency _L [HZ] of its passband.
As [Ω], its primary inductance L ₁ [H]
roughly satisfies 2π _L L ₁ = Z ₁ , and in the same way, the leakage inductance L′ ₁ [H] seen from the primary side is 2π _H L′ ₁ due to the upper limit frequency _H [HZ].
= Z ₁ , and in both cases this is
This is the frequency band with a 3dB drop. In addition, the primary and secondary turns ratio n ₁ :n ₂ is the impedance of the primary and secondary
It is well known that Z ₁ and Z ₂ are determined by the relationship n ₁ /n ₂ =√ _{1 2} . Here, the call signal is in the voice band, and its upper frequency limit is approximately _3KHz .
That's about it. On the other hand, in order to prevent mutual influence with speech signals, the lower limit frequency ' _L of the transmission band of the control information signal is often separated by about ' _L ≧10' _H.

The impedance in the speech signal band of the inductance L ₁ [H] on the primary side of the transformer shown in Fig. 3 is 2π′ _H L ₁ = [Ω], which is equal to the impedance Z ₁ (=2π _(L L ₁ ) is sufficiently small compared to (the ratio is ′ _H / _L ). Therefore, from the viewpoint of the speech signal passing through the primary side of the transformer 11, it can be equivalently considered as shown in Fig. 4, and the primary winding _L1 can be regarded as a mere high-frequency choke, forming a kind of LPF. Therefore, the control information signal is attenuated by the ratio of ' _H / _L with respect to the speech signal. In addition, regarding the induction of a speech signal to the secondary side, even if we set the upper limit frequency of the speech signal ′ _H , 2π′ _H L ₁ <<Z ₁ , 2π′ _H L′
₁ <<
Z ₁ , and here again, in addition to the constant loss as a transformer, there is an increase in loss equal to the ratio of ′ _H / _L , and the speech signal to the secondary side is sufficiently attenuated, and the influence on the control information signal is will not be given.

On the other hand, since the transformer itself is designed in the control information signal band, the control information signal is induced to be transmitted to the secondary side with only constant loss as a transformer, which does not need explanation.

Furthermore, when transmitting and receiving power supply current from the primary side of the transformer 11, since the transformer 11 is a high frequency transformer, the number of turns on the primary side is small, so it is possible to wind a thick wire, and the inductance Since L ₁ is also small, there is little influence from DC magnetization of the transformer, and the transformer does not become larger.

As described above, according to the present invention, there is no need to use separate LPFs, HPFs, etc. as in the past.
Since the purpose can be achieved with only one small transformer, the configuration becomes simple and the economical effect becomes large. Furthermore, according to the present invention, since the chiyoke coil inserted into the power supply acts after passing through the primary side of the transformer, it is only necessary to consider the speech signal (voice) band, so it does not cause a load on the control information signal band. First, it has the advantage that it can be small and simple.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an example of a configuration using a conventional filter, FIG. 2 is a circuit diagram including blocks showing an embodiment of the present invention, and FIG. 3 is a circuit for explaining the configuration of a transformer used in the present invention. 4 are equivalent circuits of the transformer used in the present invention as seen from a speech signal.

Claims (1)

[Claims] 1. In a telephone device configured to multiplex and transmit a call signal, a power supply current, and a control information signal in a frequency band sufficiently higher than the call signal by multiple telephones connected to a pair of lines, the control A transformer is provided that uses the frequency band of the information signal as the transmission frequency band between the primary and secondary sides, and the primary sides of the transformer are separated from each other at a midpoint potential.
The terminal of the two windings at the midpoint potential is connected to the communication circuit for transmitting and receiving the communication signal, and is also connected to the power supply circuit for the power supply current via the choke coil, and the terminal at the midpoint potential of the two windings is connected to the communication circuit for transmitting and receiving the communication signal. A connection system for a telephone device, characterized in that both end terminals of the primary side except for the terminals are connected to the line, and the secondary side of the transformer is connected to the transmission/reception circuit for the control information signal.