SU30732A1 - Device for multiple and secret telephony - Google Patents

Description

As is well known, for a normal telephone conversation, it is required to transmit along the line and receive in the receiving apparatus a spectrum of frequencies from 300 periods per second to 2400 periods per second, i.e. range of 2100 individual frequencies. When allocating certain frequency bands from this range, speech clarity decreases.

However, in individual cases, it may be advisable to agree on a slight decrease in the spectrum of transmitted frequencies and, therefore, to a certain deterioration in the quality of telephone transmission, if it is possible to transmit additional conversation over the existing circuits. In addition, such a transmission may be performed for secret transmission purposes.

Such a device is proposed for multiple and secret telephony, in which, according to the invention (1 K), in order to transmit three conversations in two chains, filters are transmitted to transmit each conversation, passing only part of the audio frequencies, namely: for one conversation, low and medium audio frequencies, for the other - medium and high sound frequencies and for the third - only low and high without middle frequencies.

In FIG. 1 (a, &, c) schematically depicts a proposed device for transmitting three conversations to two chains; FIG. 2 (a, b, c) t-device for transmitting four conversations to three chains.

Devices that make it possible to transmit can be designed for use in such cases. talk on m chain

The basic idea of these devices is to divide the total number in t (d- / d) of individual frequencies into t - {- 1 parts, using each part to transmit one regg.

By / J and / d, here, is meant the highest and lowest of the transmitted frequencies, respectively. Usually these frequencies, as already mentioned, are /, - 2400 periods per second and / d - 300 periods per second.

The number of frequencies included in each of the m- parts is chosen depending on the desired quality of a conversation (see Collard, Electrical Communication, January 1930).

The implementation of this idea is carried out with the help of electrical frequency filters. Three options are offered for this.

In the first embodiment (Fig. 1a and 2a)

The devices for transmitting / ha-f-1 conversations in tons are made up of 2 filters that pass each defined frequency band, each pair of heelters has one common border frequency. The symbols /, / i, / 2, etc. in the drawings indicate the border frequencies of the filters, and under these symbols are the numbers of the approximate spectrum of frequencies transmitted by this filter.

In the second variant (Fig. 1st and 2nd), the devices contain a group of filters that let in low frequencies and a group of filters and filters that pass through high frequencies (each of the filters of the first group has a border frequency equal to the frequency of the corresponding filter of the second group), and t filters that pass each band from / to /. In the third variant (Figs. 1c and 2c), the device contains a group and t filters L, each delaying certain frequency bands, and a group of t filters K, each passing through the corresponding lengths of frequencies (the bands of each filter of the first group are identical to the bands appropriate filter in the group).

Similarly, devices can be made to transmit five conversations on four chains, etc., in the jumbo case, to transmit conversations on a / ha chain.

With regard to the passage of the call. For the telephone system in question, the call is made for those calls using the same tools that would have been used if the circuits were not used by this System, and for the additional (/ and -) 1) -th You have to use a tone call (with the appropriate frequency).

These devices can be applied on the main, phantom and high frequency circuits (in the latter case, the devices are turned on on the low frequency side).

In this connection, it may be appropriate to use these devices to get an additional fifth conversation on a circuit with one conversation.

low frequency and three high frequency conversations. If for this fifth conversation the frequency band is satisfied for 1200 periods (for the purpose of applying, for example, this conversation for business purposes), then from each conversation one will have to allocate on average

frequency range of periods

which should not be particularly reflected in the quality of the main conversations.

In some cases, it may be advisable to use the devices described here using them at certain intervals; devices (keys) can be used for this purpose, which can quickly turn on and off these devices.

It should be noted that with the proposed compaction of circuits, the secrecy of telephone transmission is achieved in a certain way, since if you simultaneously conduct several conversations, direct eavesdropping on any circuit does not produce any results, since the currents of several conversations simultaneously flow through this circuit.

The subject matter of the invention.

Claims (2)

1. A device for multiple and secret telephony, characterized in that in order to transmit three conversations in two circuits, filters are transmitted to transmit each burglar, passing only part of the audio frequencies, namely: for one conversation, low and medium frequencies, for the other one has medium and high sound frequencies and for the third one only low and high frequencies without middle frequencies (Fig. 1a, Ib, 1c). 2. A device change according to claim 1, characterized in that for the purpose of transmitting / ha- | -11 words on two chains, filters are applied, passing through, respectively, low with medium frequencies and medium with high, and for the rest, for each of them there are two high and low frequencies without medium frequencies. phage.P. fng.1 &. , /WITH Fig.P. S -. ./WITH. 1 3fS-ftfi