The use of high coercivity media in the form of magnetic tape is well known in the art. To record on high coercivity tape, it is necessary that the field strength at the recording gap be greater than the coercivity of the medium. Because the recording field at the record head gap falls off with distance, it is essential when recording on high coercivity media that intimate head/tape contact be achieved. When such media is in the form of a flexible tape, intimate contact between the tape and the head gap can be assured by adequate wrap of the tape over the head surface in the contact region. Dual gap applications, such as read after write, or write after read, do not present severe problems with respect to tape/head contact at the dual gaps, because the tape flexibility allows adequate wrap to be achieved over both the read and record gaps.

The use of magnetic cards in credit card and automatic banking operations is becoming increasingly common. The need for maintaining integrity of the data in these applications requires that the magnetic medium must be immunized against accidental erasure or intentional overwriting. This, in turn, translates into a requirement for very high coercivity magnetic media. Typically, in the art, the card has a

prerecorded track which is read by a reading station to identify the account number of the card holder during a transaction. In such applications, the reading station head has only a single gap which must contact the card, and head/media contact may be accomplished by mechanical positioning of the head relative to the card surface. In applications where a dual gap head structure is required, i.e. in a read after write or a write after read system, the problem becomes more difficult because the rigidity of the card precludes wrapping both gaps by the media as is possible when using flexible tape. The problem becomes even more difficult in the case where the card is of a high coercivity medium and intimate contact during recording, as well as reading, is a mus .

BRIEF DESCRIPTION OF THE DRAWINGS The invention will be described in relation to the drawings of which: Fig. 1 is a perspective view of a magnetic head assembly in accordance with the invention, and Fig. 2 is an expanded view of the magnetic elements of the head assembly of Fig. 1. SUMMARY OF THE INVENTION A dual gap head assembly for writing after reading a high coercivity magnetic card comprises a structure having three projecting pads for contacting the magnetic surface of the card. The pads are of equal heights, and the bottom flat surfaces of the pads which contact the card are coplanar. The pads are arranged in a tripod configuration, and as three points determine a plane, the bottom pad surfaces provide an intimate and stable mating with the magnetic surface when they are in contact with the plane of the card. Additionally, the leading and

trailing edges of the pads are tapered to preclude gouging of the magnetic surface of the card as the head traverses the card.

The magnetic portion of the head consists of two inline heads; a write head having a wide write track and a contiguous read head having a narrower track whose center line is aligned with the center line of the write track. Because the magnetic cards must interchangeably work with many card readers/ writers, the wider write than read track provides a margin of safety against mechanical tolerance buildup that may result in mistracking with consequential misreading of a previously recorded data track. The gap lines of both heads are located in the plane of the bottom surface of one of the pads. In order to attain intimate contact of both the read gap and the write gaps with the rigid high coercivity magnetic surface of the card, the plane in which they are located is of minimal area and the gaps are positioned in close proximity to each other, insuring simultaneous contacting of the gaps with the medium. To adequately write on the high coercivity medium of the card, the core of the write head is fabricated from a material of high saturation magnetization which allows generating a field of over 5000 oersteds at the write gap without saturating the core.

DESCRIPTION OF THE INVENTION Referring to Fig. 1, a magnetic head assembly is fabricated utilizing a non-magnetic enclosure 10, i.e., aluminum, for containing the magnetic elements of the head assembly. Projecting from one surface 11 of the block 10, are three pads 12, 14, 16. The pads 12, 14, 16, are positioned in a tripod arrangement, and are provided with coplanar

surfaces 18, 20, 22. The planar surface 18 of the pad 12 is larger in area than the surfaces 20, 22 of the pads 14 and 16. The read gap 24 and the write gap 26 of read and write heads contained in the enclosure 10 are located in the surface 18 of the pad 12, and the pads 14, 16 serve as the two other legs of the tripod to provide mechanical stability of the medium/gap contact when the head assembly is in position against a planar rigid magnetic card. The planar surfaces 20, 22 of the pads 14, 16 are approximately 6.4 x 10 (-4) sq. in., and the surface 18 of the pad 12 is approximately 16.3 x 10 ( ^v -4)' sq. in. , effectively providing stable three point contact for the read and write gaps 24, 26 in contacting the medium at the head/card interface.

When used with an associated transport apparatus to provide relative motion between the heads and a card, the head assembly moves relative to the card in the direction indicated by an arrow, 28. In order to prevent gouging of the magnetic surface of the card as the head assembly traverses the card, the leading and trailing edges of the pads 12, 14, 16 are tapered; the pad 12 having the tapers 30, 32, the pad 14, the tapers 34, 36 and the pad 16, the tapers 38, 40. It will also be noted that the tapers allow control of the areas of the planar bottoms of the pads 12, 14, 16, whereby the areas may be minimized to approximate three point stable contact between the pads and the card. Referring to Fig. 2, the write head 42 comprises a laminated core 44, a back bar 46, and a winding 48. The core 44 is fabricated from a Si-Fe ^' alloy having a magnetization saturation greater than 20,000 gauss. The read head 50 comprises a laminated core 53, a back bar 54 and a winding 56. The write

head has a track width approximately .008" and the read head, whose track width centerline is aligned with that of the write head, has a track width approximately .004" wide. The write head 42 and the read head 50 are so mounted that their respective gaps 26, 24 are located in the planar surface 18 of the pad 12 with the intergap distance approximately equal to .070".

The invention has been described in detail with particular reference to preferred embodiments thereof, but it will be understood that variations and modifications can be effected within the spirit and scope of the invention.