JPS58205904A - Head switching circuit - Google Patents

Abstract

PURPOSE:To locate a switching circuit near a head amplifier, by using two relays for switching so as to short-circuit a channel not in use. CONSTITUTION:The 1st switching relay 7 connecting each one terminal of each coil to, e.g. one output terminal 5, and the 2nd switching relay 8 connecting one terminal of each coil to the other output terminal 6 selectively, are provided. Then, the relays are used to short-circuit and to ground a channel not in use for the purpose of connection so as not to have the effect of the channel not in use. Thus, the arrangement is attained for a rotary transformer 3 and the relays 7, 8 so as to use shield wires among them. That is, the switching circuit is located near the head amplifier 9.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a head discrete circuit used in a magnetic recording/reproducing device.

The video head of a magnetic recording/reproducing device is now made into a four-head video head in order to optimize the image quality and special playback in the tlli semi-mode (2 hours) and long-time mode (6 hours).

Conventional 4-head switching circuits use one relay to switch the head output from a rotary transformer and output it to the head-up, or each head amplifier has its own head amplifier, and its output is switched by a relay or the like to output the brightness chroma. There is a method for outputting to the circuit. The first arrival method is tg issue ILIOμV
Since switching is performed at a low output level, it is extremely susceptible to external noise. Adequate shielding of the switching circuit is therefore essential, and shielded wires are generally used to couple the switching circuit to the head amplifier. Head inductance and shield wire 1 valley Sumire rod AMP human power valley It
etc., the highest frequency of the tone frequency (4,5 to 5 iAHz
) to compensate for the vibration caused by the tape head thread. For this reason, the capacity of the shielded wire cannot be increased, and it is necessary to install a switching circuit board near the drum.The latter method uses two identical head amplifiers, which is disadvantageous in terms of cost and space.

This invention uses two relays to perform switching and short-circuit the unused channel side, thereby preventing the influence of the shielded wire of the unused channel and making it possible to bring the switching circuit close to the head amplifier. It is something.

Figure 1 shows a conventional switching circuit using one relay (
However, only the R channel is shown). Video head (Sk
', l, EP~2) is the signal from the rotary transformer (3
), the zP open signal is output at relay (4)K (5).
) to the head amplifier. One terminal (6
) should be shorted to ground. In this circuit, the signal line is 1 μm on the unused channel (sp) side, which is uncircuited, so a ``floating valley'' on the short-circuited channel side is added. Therefore, in this case, the switching circuit cannot be placed very far from the transformer, and it is necessary to install a board for the switching circuit near the drum 1 and then connect it to the head amplifier 9 via a shielded wire. Furthermore, the signal level is very low. Because of this, 70 base grudges also require a sufficient shield.

FIG. 2 shows an embodiment of the present invention. This embodiment uses relays to short-circuit and ground unused channels, and also connects unused channels to signal lines. Since the connection is free from interference, it is convenient to use a shielded wire between the rotary transformers (melee (7) and (8)).In other words, the switching circuit can be brought near the head amplifier 9, and the switching circuit There is no need to use a special board or shield case for
' Note that the pair of relays (7) and (8) are not limited to mechanical type relays, but equivalent young fruits can be obtained even if electronic circuit type relays are used.

As described above, the present invention switches a pair of heads using two relays, short-circuits the unused channels of the 1st head, and connects the 1d line with the 1st head without being affected by the unused channel. By doing this, &fi can be achieved by placing the switching circuit near the one/doing to the entire switching circuit.

With this Y, there is no need to specially provide a board shield case for the t7I conversion circuit.

Compared to the method using two head amplifiers, it is advantageous in terms of cost and space, and is industrially 1. Ili value should be large 6°

[Brief explanation of the drawing]

Figure 1 shows a rice-produced relay and a switching circuit with an 11th direction F. Figure 2 is a switching circuit diagram according to an embodiment of the present invention. In the figure 1.2 ~ video head, 3 ~ rotary transformer, 4
．． 7.8 - Relay, 5.6 - Output terminal. Agent Tameno Layer - Figure 1 I 7 Figure 2 7 I

Claims (1)

[Claims] A pair of coils each generating a head output, a pair of output terminals for selectively outputting each of the head outputs, and a first switch for selectively connecting one end of each of the coils to one of the output terminals. a head switching circuit comprising a relay, a second switching relay for selectively connecting one end of each of the coils to the other of the output terminals, and connecting the other end of each of the coils to the other of the output terminals; .